ALL ABOUT COMPUTERS

30) SANYO ITEMS

2009-06-20T06:05:00.007-07:00

SANYO Electric Co., Ltd. (三洋電機株式会社, San'yō Denki Kabushiki-gaisha?) (TYO: 6764, NASDAQ: SANYY) is a major electronics company and member of the Fortune 500 whose headquarters is located in Moriguchi, Osaka prefecture, Japan. Sanyo targets the middle of the market and has over 324 offices and plants worldwide[citation needed], together employing more than 11,000 employees.

On November 2, 2008, Sanyo and Panasonic announced that they have agreed on the main points of a proposed buyout that would make Sanyo a subsidiary of Panasonic and a formal announcement of the acquisition was made on Sanyo's web site on December 19, 2008.Panasonic plans to make an offer in late July or early August and make Sanyo a subsidiary in September.

Corporate culture
Sanyo utilizes an extensive socialization process for new employees, so that they will be acclimatized to Sanyo's corporate culture. New employees take a five-month course during which they eat together and share company-provided sleeping accommodation. They learn everything from basic job requirements to company expectations for personal grooming and the appropriate way in which to address their coworkers and superiors.

History
Sanyo was founded when Toshio Iue (井植歳男 Iue Toshio, 1902-1969), the brother-in-law of Konosuke Matsushita and also a former Matsushita employee, was lent an unused Matsushita plant in 1947 and used it to make bicycle generator lamps. Sanyo was incorporated in 1950 and in 1952 it made Japan's first plastic radio and in 1954 Japan's first pulsator-type washing machine. The company's name means three oceans in Japanese, referring to the founder's ambition to sell their products worldwide, across the Atlantic, Pacific and Indian oceans.

Technologically Sanyo has had good ties with Sony, supporting the Betamax video format from invention until the mid 1980s (the best selling video recorder in the UK in 1983 was the Sanyo VTC5000), and later being an early adopter of the highly successful Video8 camcorder format. More recently, though, Sanyo decided against supporting Sony's format, the Blu-ray Disc, and instead gave its backing to Toshiba's HD DVD. This was ultimately unsuccessful, however, as Sony's Blu-ray triumphed.

In North America, Sanyo manufactures CDMA cellular phones exclusively for Sprint-Nextel corporation's Sprint PCS brand in the United States, and for Bell Mobility in Canada. For three consecutive years, Sanyo received the J.D. Power and Associates award for having the highest overall satisfaction out of the eight most popular mobile phone manufacturers. However in 2005 Sanyo tied with LG for this position.

The 2004 Chūetsu earthquake severely struck Sanyo's semiconductor plant and as a result Sanyo recorded a huge financial loss for that year. The 2005 fiscal year financial results saw a 205 billion yen net income loss. The same year the company announced a restructuring plan called the Sanyo Evolution Project, launching a new corporate vision to make the corporation into an environmental company, plowing investment into strong products like rechargeable batteries, solar photovoltaics, air conditioning, hybrid car batteries in a joint venture with Honda Motor Co. Ltd. (two firms would develop a nickel hydrogen battery) and key consumer electronics such as the Xacti camera, projectors and mobile phones.

SANYO CAMERAS

SANYO WEBCAMS

SANYO TVs

29) SONY ITEMS

2009-06-20T06:05:00.006-07:00

Sony Corporation (ソニー株式会社, Sonī Kabushiki Gaisha?) is a multinational conglomerate corporation headquartered in Minato, Tokyo, Japan, and one of the world's largest media conglomerates with revenue exceeding ¥ 7.730.0 trillion, or $78.88 billion U.S. (FY2008). Sony is one of the leading manufacturers of electronics, video, communications, video game consoles, and information technology products for the consumer and professional markets. Its name is derived from sonus, the Latin word for sound.

Sony Corporation is the electronics business unit and the parent company of the Sony Group, which is engaged in business through its five operating segments—electronics, games, entertainment (motion pictures and music), financial services and other. These make Sony one of the most comprehensive entertainment companies in the world. Sony's principal business operations include Sony Corporation (Sony Electronics in the U.S.), Sony Pictures Entertainment, Sony Computer Entertainment, Sony Music Entertainment, Sony Ericsson, and Sony Financial. As a semiconductor maker, Sony is among the Worldwide Top 20 Semiconductor Sales Leaders. The company's slogan is Sony. Like no other.

History
In 1945, after World War II, Masaru Ibuka started a radio repair shop in a bombed-out building in Tokyo. The next year, he was joined by his colleague Akio Morita and they founded a company called Tokyo Tsushin Kogyo K.K., which translates in English to Tokyo Telecommunications Engineering Corporation. The company built Japan's first tape recorder called the Type-G.

Masaru Ibuka, the co-founder of Sony

In the early 1950s, Ibuka traveled in the United States and heard about Bell Labs' invention of the transistor. He convinced Bell to license the transistor technology to his Japanese company. While most American companies were researching the transistor for its military applications, Ibuka looked to apply it to communications. Although the American companies Regency and Texas Instruments built the first transistor radios, it was Ibuka's company that made them commercially successful for the first time. In August 1955, Tokyo Telecommunications Engineering released the Sony TR-55, Japan's first commercially produced transistor radio. They followed up in December of the same year by releasing the Sony TR-72, a product that won
favor both within Japan and in export markets, including Canada, Australia, the Netherlands and Germany. Featuring six transistors, push-pull output and greatly improved sound quality, the TR-72 continued to be a popular seller into the early sixties.

In May 1956, the company released the TR-6, which featured an innovative slim design and sound quality capable of rivaling portable tube radios. It was for the TR-6 that Sony first contracted "Atchan", a cartoon character created by Fuyuhiko Okabe, to become its advertising character. Now known as "Sony Boy", the character first appeared in a cartoon ad holding a TR-6 to his ear, but went on to represent the company in ads for a variety of products well into the mid-sixties. The following year, 1957, Tokyo Telecommunications Engineering came out with the TR-63 model, then the smallest (112 × 71 × 32 mm) transistor radio in commercial production. It was a worldwide commercial success.

University of Arizona professor Michael Brian Schiffer, Ph.D., says, "Sony was not first, but its transistor radio was the most successful. The TR-63 of 1957 cracked open the U.S. market and launched the new industry of consumer microelectronics." By the mid 1950s, American teens had begun buying portable transistor radios in huge numbers, helping to propel the fledgling industry from an estimated 100,000 units in 1955 to 5,000,000 units by the end of 1968.

Sony's headquarters moved to Minato, Tokyo from Shinagawa, Tokyo around the end of 2006.

Sony products, technologies and proprietary formats
Sony has historically been notable for creating its own in-house standards for new recording and storage technologies instead of adopting those of other manufacturers and standards bodies. The most infamous of these was the videotape format war of the early 1980s, when Sony marketed the Betamax system for video cassette recorders against the VHS format developed by JVC. In the end, VHS gained critical mass in the marketplace and became the worldwide standard for consumer VCRs and Sony adopted the format. While Betamax is for all practical purposes an obsolete format, a professional-oriented component video format called Betacam that was derived from Betamax is still used today, especially in the film and television industry.

In 1968 Sony introduced the Trinitron brand name for its line of aperture grille cathode ray tube televisions and (later) computer monitors. Trinitron displays are still produced, but only for markets such as Pakistan, Bangladesh, India and China. Sony discontinued the last Trinitron-based television set in the USA Spring of 2007. Trinitron computer monitors were discontinued in 2005.

Sony launched the Betamax videocassette recording format in 1975. In 1979 the Walkman brand was introduced, in the form of the world's first portable music player.

1982 saw the launch of Sony's professional Betacam videotape format and the collaborative Compact Disc format. In 1983 Sony introduced 90 mm micro diskettes (better known as 3.5-inch (89 mm) floppy disks), which it had developed at a time when there were 4" floppy disks and a lot of variations from different companies to replace the then on-going 5.25" floppy disks. Sony had great success and the format became dominant; 3.5" floppy disks gradually became obsolete as they were replaced by current media formats. In 1983 Sony launched the MSX, a home computer system, and introduced the world (with their counterpart Philips) to the Compact Disc or CD. In 1984 Sony launched the Discman series which extended their Walkman brand to portable CD products. In 1985 Sony launched their Handycam products and the Video8 format. Video8 and the follow-on hi-band Hi8 format became popular in the consumer camcorder market. In 1987 Sony launched the 4 mm DAT or Digital Audio Tape as a new digital audio tape standard.

SONY MONITORS
This extension of the monitor provides a ready-made area for keeping Post-it® notes in one place while also sporting a handy groove which is ideal for holding pens.

Available in size screens with both digital (DVI-D) and analogue (HD-15) interfaces as standard, the E Series redefines the home or work office and helps make sure desks remain tidy and organised.

The Sony personal computer displays range was brought under Sony Europe’s IT Peripherals umbrella in April 2006 alongside the storage products to ensure a dedicated refocus on these products through indirect channels. The E Series is the first of the new range of displays to be made available in this way and the exciting new style is designed to attract attention.

SONY TELEVISIONS

SONY CAMERAS

SONY CELL SETS

28) COMPUTER 'S POWER SUPPLY

2009-06-20T06:05:00.005-07:00

Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others.

Electrical power supplies
This term covers the power distribution system together with any other primary or secondary sources of energy such as:

Conversion of one form of electrical power to another desired form and voltage. This typically involves converting 120 or 240 volt AC supplied by a utility company (see electricity generation) to a well-regulated lower voltage DC for electronic devices. Low voltage, low power DC power supply units are commonly integrated with the devices they supply, such as computers and household electronics. For other examples, see switched-mode power supply, linear regulator, rectifier and inverter (electrical).
Batteries
Chemical fuel cells and other forms of energy storage systems
Solar power
Generators or alternators (particularly useful in vehicles of all shapes and sizes, where the engine has torque to spare, or in semi-portable units containing an internal combustion engine and a generator) (For large-scale power supplies, see electricity generation.)
Constraints that commonly affect power supplies are the amount of power they can supply, how long they can supply it without needing some kind of refueling or recharging, how stable their output voltage or current is under varying load conditions, and whether they provide continuous power or pulses.

The regulation of power supplies is done by incorporating circuitry to tightly control the output voltage and/or current of the power supply to a specific value. The specific value is closely maintained despite variations in the load presented to the power supply's output, or any reasonable voltage variation at the power supply's input. This kind of regulation is commonly categorized as a Stabilized power supply.

Power supply types
Power supplies for electronic devices can be broadly divided into linear and switching power supplies. The linear supply is a relatively simple design that becomes increasingly bulky and heavy for high current devices; voltage regulation in a linear supply can result in low efficiency. A switched-mode supply of the same rating as a linear supply will be smaller, is usually more efficient, but will be more complex.

Battery power supply
A battery is a type of linear power supply that offers benefits that traditional line-operated power supplies lack: mobility, portability, and reliability. A battery consists of multiple electrochemical cells connected to provide the voltage desired.

The most commonly used dry-cell battery is the carbon-zinc dry cell battery. Dry-cell batteries are made by stacking a carbon plate, a layer of electrolyte paste, and a zinc plate alternately until the desired total voltage is achieved. The most common dry-cell batteries have one of the following voltages: 1.5, 3, 6, 9, 22.5, 45, and 90. During the discharge of a carbon-zinc battery, the zinc metal is converted to a zinc salt in the electrolyte, and magnesium dioxide is reduced at the carbon electrode. These actions establish a voltage of approximately 1.5 V.

The lead-acid storage battery may be used. This battery is rechargeable; it consists of lead and lead/dioxide electrodes which are immersed in sulfuric acid. When fully charged, this type of battery has a 2.06-2.14 V potential. During discharge, the lead is converted to lead sulfate and the sulfuric acid is converted to water. When the battery is charging, the lead sulfate is converted back to lead and lead dioxide.

A nickel-cadmium battery has become more popular in recent years.This battery cell is completely sealed and rechargeable. The electrolyte is not involved in the electrode reaction, making the voltage constant over the span of the batteries long service life. During the charging process, nickel oxide is oxidized to its higher oxidation state and cadmium oxide is reduced. The nickel-cadmium batteries have many benefits. They can be stored both charged and uncharged. They have a long service life, high current availabilities, constant voltage, and the ability to be recharged.

Linear power supply
An AC powered linear power supply usually uses a transformer to convert the voltage from the wall outlet (mains) to a different, usually a lower voltage. If it is used to produce DC, a rectifier is used. A capacitor is used to smooth the pulsating current from the rectifier. Some small periodic deviations from smooth direct current will remain, which is known as ripple. These pulsations occur at a frequency related to the AC power frequency (for example, a multiple of 50 or 60 Hz).

The voltage produced by an unregulated power supply will vary depending on the load and on variations in the AC supply voltage. For critical electronics applications a linear regulator will be used to stabilize and adjust the voltage. This regulator will also greatly reduce the ripple and noise in the output direct current. Linear regulators often provide current limiting, protecting the power supply and attached circuit from overcurrent.

Adjustable linear power supplies are common laboratory and service shop test equipment, allowing the output voltage to be set over a wide range. For example, a bench power supply used by circuit designers may be adjustable up to 30 volts and up to 5 amperes output. Some can be driven by an external signal, for example, for applications requiring a pulsed output.

The simplest DC power supply circuit consists of a single diode and resistor in series with the AC supply. This circuit is common in rechargeable flashlights

A home-made linear power supply (used here to power amateur radio equipment

AC/ DC supply
In the past, mains electricity was supplied as DC in some regions, AC in others. A simple, cheap linear power supply would run directly from either AC or DC mains, often without using a transformer. The power supply consisted of a rectifier and a capacitor filter. The rectifier was essentially a conductor, having no sudden effect when operating from DC.

Switched-mode power supply
A switched-mode power supply (SMPS) works on a different principle. AC mains input is directly rectified without the use of a transformer, to obtain a DC voltage. This voltage is then sliced into small pieces by a high-speed electronic switch. The size of these slices grows larger as power output requirements increase.

The input power slicing occurs at a very high speed (typically 10 kHz — 1 MHz). High frequency and high voltages in this first stage permit much smaller step down transformers than are in a linear power supply. After the transformer secondary, the AC is again rectified to DC. To keep output voltage constant, the power supply needs a sophisticated feedback controller to monitor current draw by the load.

Modern switched-mode power supplies often include additional safety features such as the crowbar circuit to help protect the device and the user from harm. In the event that an abnormal high current power draw is detected, the switched-mode supply can assume this is a direct short and will shut itself down before damage is done. For decades PC computer power supplies have also provided a power good signal to the motherboard which prevents operation when abnormal supply voltages are present.

Switched mode power supplies have an absolute limit on their minimum current output. They are only able to output above a certain power level and cannot function below that point. In a no-load condition the frequency of the power slicing circuit increases to great speed, causing the isolation transformer to act as a tesla coil, causing damage due to the resulting very high voltage power spikes. Switched-mode supplies with protection circuits may briefly turn on but then shut down when no load has been detected. A very small low-power dummy load such as a ceramic power resistor or 10 watt light bulb can be attached to the supply to allow it to run with no primary load attached.

Power factor has become a recent issue of concern for computer manufacturers. Switched mode power supplies have traditionally been a source of power line harmonics and have a very poor power factor. Many computer power supplies built in the last few years now include power factor correction built right into the switched-mode supply, and may advertise the fact that they offer 1.0 power factor.

By slicing up the sinusoidal AC wave into very small discrete pieces, the portion of the alternating current not used stays in the power line as very small spikes of power that cannot be utilized by AC motors and results in waste heating of power line transformers. Hundreds of switched mode power supplies in a building can result in poor power quality for other customers surrounding that building, and high electric bills for the company if they are billed according to their power factor in addition to the actual power used. Filtering capacitor banks may be needed on the building power mains to suppress and absorb these negative power factor effects.

A computer's switched mode power supply unit

Programmable power supply
Programmable power supplies are those in which the output voltage can be varied remotely. One possible option is digital control by a computer interface. Variable properties include voltage, current, and frequency. This type of supply is composed of a processor, voltage/current programming circuits, current shunt, and voltage/current read-back circuits.

Programmable power supplies can furnish DC, AC, or both types of output. The AC output can be either single-phase or three-phase. Single-phase is generally used for low-voltage, while three-phase is more common for high-voltage power supplies.

When choosing a programmable power supply, several specifications should be considered. For AC supplies, output voltage, voltage accuracy, output frequency, and output current are important attributes. For DC supplies, output voltage, voltage accuracy, current, and power are important characteristics. Many special features are also available, including computer interface, overcurrent protection, overvoltage protection, short circuit protection, and temperature compensation. Programmable power supplies also come in a variety of forms. Some of those are modular, board-mounted, wall-mounted, floor-mounted or bench top.

Programmable power supplies are now used in many applications. Some examples include automated equipment testing, crystal growth monitoring, and differential thermal analysis

Uninterruptible power supply
An Uninterruptible Power Supply (UPS) takes its power from two or more sources simultaneously. It is usually powered directly from the AC mains, while simultaneously charging a storage battery. Should there be a dropout or failure of the mains, the battery instantly takes over so that the load never experiences an interruption. Such a scheme can supply power as long as the battery charge suffices, e.g., in a computer installation, giving the operator sufficient time to effect an orderly system shutdown without loss of data. Other UPS schemes may use an internal combustion engine or turbine to continuously supply power to a system in parallel with power coming from the AC mains. The engine-driven generators would normally be idling, but could come to full power in a matter of a few seconds in order to keep vital equipment running without interruption. Such a scheme might be found in hospitals or telephone central offices.

High-voltage power supply
High voltage refers to an output on the order of hundreds or thousands of volts. High-voltage power supplies use a linear setup to produce an output voltage in this range.

When choosing a high-voltage power supply, there are several options to consider. Some of these are maximum current, maximum power, maximum voltage, output polarity, user interface, and style. The first four of these characteristics of course depend upon the supply's intended application. There are many available types of user interfaces. For example, the interface may be local in the form of a digital meter, or analog meter. Also, the interface can be remote, as in a computer connection. Numerous styles of high-voltage power supplies are also manufactured. Available models come in printed circuit board mount, open frame (as designed to be incorporated into an instrument), and rack mount. Models with multiple outputs can also be found

Voltage multipliers
Voltage multipliers, as the name implies, are circuits designed to multiply the input voltage. The input voltage may be doubled (voltage doubler), tripled (voltage tripler), quadrupled (voltage quadrupler), etc. Voltage multipliers are also power converters. An AC input is converted to a higher DC output. These circuits allow high voltages to be obtained using a much lower voltage AC source.

Typically, voltage multipliers are composed of half-wave rectifiers, capacitors, and diodes. For example, a voltage tripler consists of three half-wave rectifiers, three capacitors, and three diodes. Full-wave rectifiers may be used in a different configuration to achieve even higher voltages. Also, both parallel and series configurations are available. For parallel multipliers, a higher voltage rating is required at each consecutive multiplication stage, but less capacitance is required. The voltage capability of the capacitor limits the maximum output voltage.

Voltage multipliers have many applications. For example, voltage multipliers can be found in everyday items like televisions and photocopiers. Even more applications can be found in the laboratory, such as cathode ray tubes, oscilloscopes, and photomultiplier tubes.

A modern computer power supply is a switched-mode supply designed to convert 110-240 V AC power from the mains supply, to several output both positive (and historically negative) DC voltages in the range + 12V,-12V,+5V,+5VBs and +3.3V. The first generation of computers power supplies were linear devices, but as cost became a driving factor, and weight became important, switched mode supplies are almost universal.

The diverse collection of output voltages also have widely varying current draw requirements, which are difficult to all be supplied from the same switched-mode source. Consequently most modern computer power supplies actually consist of several different switched mode supplies, each producing just one voltage component and each able to vary its output based on component power requirements, and all are linked together to shut down as a group in the event of a fault condition.

The most common modern computer power supplies are built to conform to the ATX form factor. The power rating of a PC power supply is not officially certified and is self-claimed by each manufacturer.A common way to reach the power figure for PC PSUs is by adding the power available on each rail, which will not give a true power figure. The more reputable makers advertise "True Wattage Rated" to give consumers the idea that they can trust the power advertised.

AC adapter
A linear or switched-mode power supply (or in some cases just a transformer) that is built into the top of a plug is known as a "wall wart", "power brick", "plug pack", "plug-in adapter", "adapter block", "domestic mains adapter" or just "power adapter". They are even more diverse than their names; often with either the same kind of DC plug offering different voltage or polarity, or a different plug offering the same voltage. "Universal" adapters attempt to replace missing or damaged ones, using multiple plugs and selectors for different voltages and polarities. Replacement power supplies must match the voltage of, and supply at least as much current as, the original power supply.

The least expensive AC units consist solely of a small transformer, while DC adapters include a few additional diodes. Whether or not a load is connected to the power adapter, the transformer has a magnetic field continuously present and normally cannot be completely turned off unless unplugged.

Because they consume standby power, they are sometimes known as "electricity vampires" and may be plugged into a power strip to allow turning them off. Expensive switched-mode power supplies can cut off leaky electrolyte-capacitors, use powerless MOSFETs, and reduce their working frequency to get a gulp of energy once in a while to power, for example, a clock, which would otherwise need a battery.

This type of power supply is popular among manufacturers of low cost electrical items because:

Switched mode mobile phone charger

1.Devices sold in the global marketplace don't need to be individually configured for 120 volt or 230 volt operation, just sold with the appropriate AC adapter.
2.The device itself doesn't need to be tested for compliance with electrical safety regulations. Only the adapter needs to be tested.
3.Product development becomes faster and cheaper, because the heat produced by the power supply is outside of the product.
4.The device itself can be smaller and lighter, since it does not contain the power supply.

SOME POWER SUPPLIES OF COMPUTERS

27) PHILIPS ITEMS

2009-06-20T06:05:00.004-07:00

Koninklijke Philips Electronics N.V. (Royal Philips Electronics Inc.), most commonly known as Philips, (Euronext: PHIA, NYSE: PHG) is a Dutch electronics company.

Philips is one of the largest electronics companies in the world. In 2007, its sales were €26.79 billion. The company employs 123,800 people in more than 60 countries.

Philips is organized in a number of sectors: Philips Consumer Lifestyle (formerly Philips Consumer Electronics and Philips Domestic Appliances and Personal Care), Philips Lighting and Philips Healthcare (formerly Philips Medical Systems).

Philips headquarters in Amsterdam

History
The company was founded in 1891 by Gerard Philips, a maternal cousin of Karl Marx, in Eindhoven, the Netherlands. Its first products were light bulbs and other electro technical equipment. Its first factory remains as a museum devoted to light sculpture. In the 1920s, the company started to manufacture other products, such as vacuum tubes (also known worldwide as 'valves'), In 1927 they acquired the British electronic valve manufacturers Mullard and in 1932 the German tube manufacturer Valvo, both of which became subsidiaries. In 1939 they introduced their electric razor, the Philishave (marketed in the USA using the Norelco brand name). Also on March 11, 1927 Philips went on the air with a station called PCJ now known as Radio Netherlands. It was broadcast to the Dutch East Indies. The host of the first broadcast was Eddy Startz and from 1927 until he retired in 1969 he hosted a show called Happy Station. The only time the station went off air was when the Nazis invaded Holland. At the end of the war PCJ changed its name to Radio Netherlands and has continued broadcasting to this day.

The company was also instrumental in the revival of the Stirling engine.

On 9 May 1940, the Philips directors were informed about the German invasion of the Netherlands to take place the next day. They decided to leave the country and flee to the United States, taking a large amount of the company capital with them. Operating from the US as the North American Philips Company, they managed to run the company throughout the war. At the same time, the company itself was moved to the Netherlands Antilles (just on paper) to keep it out of German hands.

It is also believed that Philips—both before and during the war—supplied enormous amounts of electric equipment to the German occupation forces, which has led some people to think that the company collaborated with the Nazis, like many other firms in their day. However, there is no evidence to suggest that Philips itself or its management ever sympathized with the Nazis or their ideologies. The only Philips family member who did not leave the country, Frits Philips, saved the lives of 382 Jews by indicating to the Nazis that they were indispensable for the production process at Philips. In 1996, he was awarded the Yad Vashem reward by the Israeli ambassador for his actions. There is little Philips could have done to prevent the Germans from abusing their production facilities and forcing their employees to perform slave labour during the occupation. The production facility in Eindhoven was the only Dutch industrial target that was deliberately bombed by the allied forces during the war.

Postwar era
After the war the company was moved back to the Netherlands, with their headquarters in Eindhoven. Many secret research facilities had been locked and successfully hidden from the invaders, which allowed the company to get up to speed again quickly after the war.

In 1950, Philips formed Philips Records.

Philips introduced the audio Compact Cassette tape in 1963 and was wildly successful. Compact cassettes were initially used for dictation machines for office typing stenographers and professional journalists. As their sound quality improved, cassettes would also be used to record sound and became the second mass media to sell recorded music alongside vinyl records. Philips introduced the first combination portable radio and cassette recorder which is marketed as the "radiorecorder" and which is now better known as the boom box. Later the cassette was used in telephone answering machines including a special form of cassette where the tape was wound on an endless loop. The C-cassette found itself also as the first mass storage device for early personal computers in the 1970s and 1980s. Philips would also reduce the cassette size for the professional needs, first with the mini cassette and later the microcassette which were predominant dictation machines up to the advent of fully digital dictation machines.

In 1972 Philips launched the world's first home video cassette recorder, the N1500 with bulky video cassettes that could record 30 minutes or 45 minutes. Later one hour tapes were also offered. As competition came from Sony's Betamax and the VHS group of manufacturers, Philips introduced the N1700 system which allowed double length recording and for the first time would fit a 2 hour movie onto one video cassette. This idea was soon copied by the Japanese makers whose tapes were significantly cheaper. Philips made one last attempt at a new standard for video recorders with the Video 2000 system with tapes that could be used on both sides and had thus 8 hours of total recording time. As Philips only sold its systems on the PAL standard and in Europe, and the Japanese makers sold globally, the scale advantages of the Japanese proved insurmountable and Philips withdrew the V2000 system and joined the VHS Coalition.

Philips had early developments of a laser disk for selling movies but delayed its commercial launch for fear of cannibalizing its video recorder sales. Later Philips would join with Sony to launch the first commercial laser disk standard and players, and again in 1982 with Sony to launch Compact Disc. This evolved to the present day DVD, which Philips launched with Sony in 1997.

In 1991, the company's name was changed from N.V. Philips Gloeilampenfabrieken to Philips Electronics N.V. At the same time, North American Philips was formally dissolved, and a new corporate division was formed in the U.S. with the name Philips Electronics North America Corp.

In 1997 the decision was made to move the headquarters from Eindhoven to Amsterdam, along with the corporate name change to Koninklijke Philips Electronics N.V. The move was completed in 2001. Initially, the company was housed in the Rembrandt tower, but in 2002 they moved again, this time to the Breitner tower. In a sense, the move to Amsterdam can be considered a return to the company's roots, because Gerard Philips lived in Amsterdam when he came up with the idea of building a light bulb factory. He also conducted his first experiments in the field of mass production of light bulbs there, together with Jan Reesse. Philips Lighting, Philips Research, Philips Semiconductors (spun off as NXP in September 2006) and Philips Design, are still based in Eindhoven. Philips Healthcare is headquartered in both Best, Netherlands (just outside Eindhoven) and Andover, Massachusetts, United States (near Boston).

With lead-free design

With a Digital Deflection CPU, one-touch brightness enhancement, high brightness Real Flat CRT tube and ideal screen size, the 107S9 delivers an unbeatable mix of performance and value plus environment-friendly lead-free design.

Philips Philips GC4310 / Azur Precise Iron

•Steam tip Powerful shot of steam - 100g/min Drip-stop system Vertical steam Careeza soleplate High continuous steam output - upto 40g/min Automatic anti-calc system Spray function Drop resistance 350ml water tank 360 degrees swivel 3m cord for freedom of movement when ironing 2400 Watts

PHILIPS WEBCAM

Phillips are another company getting behind the 2008 VoIP trend with the launch of a range of attractive looking webcams and VoIP phones.

VoIP isn’t new but it has certainly gained more acceptance in recent years as a genuine business instrument, rather than a home application that helped people keep in touch, where the cost and novelty made up for the poor quality of the image and the restriction of the typical headset

PHILIPS LCD

NEC unveils another eco-friendly monitor that carries and ErgoDesign adjustable stand that should come in handy for people looking for eco-friendly visual solutions available in the market today. It carries an ECO Mode feature that means that power consumption is reduced.

The Intelligent Power Management and off timer features help conserve energy and reduce carbon dioxide emissions by switching to a low-power state or automatically powering down when the monitor is on, but not in use. The combination of these green technologies extends the life of the MultiSync E222W and raises the standard for green LCD displays.

Features:

1680 x 1050 native resolution in 16:10 aspect ratio
250 cd/m² brightness
Rapid Response time of 5ms
4-way ergonomic stand with 110mm height-adjust, tilt, swivel and pivot
ECO Mode and carbon footprint meter
Energy Star 5.0 and EPEAT Silver compliant
Intelligent Power Management (IPM) system and off timer
50% less power consumption and mercury content
5-setting Dynamic Video Mode (standard, text, movie, game, photo)
Multi-directional OSD NaViKey
HDCP and Windows Vista Premium-certified
NaViSet Administrator software for centralized control
Recycled packaging materials
The NEC E222W monitor has an MSRP of $269 and will become available this July.

PHILIPS TRIMMER/SHAVING MACHINE

Costco is clearing out this auto cleaning shaver for just under $50, INSTORE ONLY. Great deal that has been going on for some time and is already sold out at some places.
In BC, Bby and Richmond costco (and probably others too) still seem to have a lot left. But note that there are a lot of ppl at Costco today so it might sell out quick by tomorrow.

26) PHOTONIC COMPUTING

2009-06-20T06:05:00.003-07:00

Today's computers use the movement of electrons in-and-out of transistors to do logic. Photonic computing is intended to use photons or light particles, produced by lasers, in place of electrons. Compared to electrons, photons are much faster – light travels about 30 cm, or one foot, in a nanosecond – and have a higher bandwidth.

Details
Computers work with binary, on or off, states. A completely optical computer requires that one light beam can turn another on and off. This was first achieved with the photonic transistor, invented in 1989 at the Rocky Mountain Research Center. This demonstration eventually created a growing interest in making photonic logic componentry utilizing light interference.

Light interference is very frequency sensitive. This means that a narrow band of photon frequencies can be used to represent one bit in a binary number. Many of today's electronic computers use 64 or 128 bit-position logic. The visible light spectrum alone could enable 123 billion bit positions.

Recent research shows promise in temporarily trapping light in crystals. Trapping light is seen as a necessary element in replacing electron storage for computer logic.

While photonic computing is still seen as impractical by many[who?], research is being pushed along by strong market forces already implementing networking and, thus, creating opportunities. Recent years have seen the development of new conducting polymers which create transistor-like switches that are smaller, and 1,000 times faster, than silicon transistors.

Optical switches switch optical wavelengths. Optical switching, while not all-optical, has already become important in networking environments. 100 terabit-per-second data-handling is expected within the decade. Existing technologies include:

micro-electro-mechanical systems, or MEMS, which use tiny mechanical parts such as mirrors.
Thermo-optics technology, derived from ink-jet technology, creates bubbles to deflect light.
liquid crystal display switching changes (e.g., by filtering and rotating) the polarization states of the light.
acousto-optic modulator uses the acousto-optic effect to diffract and shift the frequency of light using sound waves (usually at radio-frequency).
photonic integrated circuits.

Optical computers
An optical computer (also called a photonic computer) is a device that uses the photons in visible light or infrared (IR) beams, rather than electric current, to perform digital computations. An electric current creates heat in computer systems, the more processing speed is needed, the more electricity is required; all this extra heat is extremely damaging to the hardware. Light however doesn't create significant amounts of heat no matter how much is used and therefore more powerful processing systems can be produced. By applying some of the advantages of visible and/or IR networks at the device and component scale, a computer might someday be developed that can perform operations 10 or more times faster than a conventional electronic computer.

Visible-light and IR beams, unlike electric currents, pass through each other without interacting. Several (or many) laser beams can be shone so their paths intersect, but there is no interference among the beams, even when they are confined essentially to two dimensions. Electric currents must be guided around each other, and this makes three-dimensional wiring necessary. Thus, an optical computer, besides being much faster than an electronic one, might also be smaller.

Some engineers think optical computing will someday be common, but most agree that transitions will occur in specialized areas one at a time. Some optical integrated circuits have been designed and manufactured. (At least one complete, although rather large, computer has been built using optical circuits.) Three-dimensional, full-motion video can be transmitted along a bundle of fibers by breaking the image into voxels. Some optical devices can be controlled by electronic currents, even though the impulses carrying the data are visible light or IR.

Optical technology has made its most significant inroads in digital communications, where fiber optic data transmission has become commonplace. The ultimate goal is the so-called photonic network , which uses visible and IR energy exclusively between each source and destination. Optical technology is employed in CD-ROM drives and their relatives, laser printers, and most photocopiers and scanners. However, none of these devices are fully optical; all rely to some extent on conventional electronic circuits and components.

Most research projects focus on replacing current computer components with optical equivalents, resulting in an optical digital computer system processing binary data. This approach appears to offer the best short-term prospects for commercial optical computing, since optical components could be integrated into traditional computers to produce an optical/electronic hybrid. Other research projects take a non-traditional approach, attempting to develop entirely new methods of computing that are not physically possible with electronics.

Optical components for binary digital computer
The fundamental building block of modern electronic computers is the transistor. To replace electronic components with optical ones, an equivalent "optical transistor" is required. This is achieved using materials with a non-linear refractive index. In particular, materials exist where the intensity of incoming light affects the intensity of the light transmitted through the material in a similar manner to the voltage response of an electronic transistor. This "optical transistor" effect is used to create logic gates, which in turn are assembled into the higher level components of the computer's CPU.

Misconceptions, challenges and prospects
Another claimed advantage of optics is that it can reduce power consumption, but an optical communication system will typically use more power over short distances than an electronic one. This is because the shot noise of an optical communication channel is greater than the thermal noise of an electrical channel which, from information theory, means that we require more signal power to achieve the same data capacity. However, over longer distances and at greater data rates the loss in electrical lines is sufficiently large that optical communications will comparatively use a lower amount of power. As communication data rates rise, this distance becomes shorter and so the prospect of using optics in computing systems becomes more practical.

A significant challenge to optical computing is that computation is a nonlinear process in which multiple signals must interact to compute the answer. Light, which is an electromagnetic wave, can only interact with another electromagnetic wave in the presence of electrons in a material and the strength of this interaction is much weaker for electromagnetic wave light than for the electronic signals in a conventional computer. This results in the processing elements for an optical computer requiring high powers and larger dimensions than for a conventional electronic computer using transistors.

Photonic logic
Photonic logic is the use of photons (light) in logic gates (AND, NAND, OR, NOR, XOR, XNOR). Photonic logic refers to the usage of light (photons) to form logic gates. Switching is obtained using nonlinear optical effects when two or more signals are combined.

Resonators are especially useful in photonic logic, since they allow a build-up of energy from constructive interference, thus enhancing optical nonlinear effects.

Other approaches currently being investigated include photonic logic at a molecular level, using photoluminescent chemicals.

Photonics
The science of photonics includes the generation, emission, transmission, modulation, signal processing, switching, amplification, detection and sensing of light. The term photonics thereby emphasizes that photons are neither particles nor waves - they are different in that they have both particle and wave nature. It basically covers all technical applications of light over the whole spectrum from ultraviolet over the visible to the near, mid and far infrared. Most applications, however, are in the range of the visible and near infrared light. The term Photonics developed as an outgrowth of the first practical semiconductor light emitters invented in the early 1960s and optical fibers developed in the 1970s.

Refraction of waves of photons (light) by a prism

25) PC HARDWARE

2009-06-20T06:05:00.002-07:00

A personal computer is made up of multiple physical components of computer hardware, upon which can be installed an operating system and a multitude of software to perform the operator's desired functions.

Typical PC hardware
Though a PC comes in many different form factors, a typical personal computer consists of a case or chassis in a tower shape (desktop) and the following parts:

Motherboard
The motherboard is the "body" of the computer. Components directly attached to the motherboard include:

The central processing unit (CPU) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan.

The chipset mediates communication between the CPU and the other components of the system, including main memory.

RAM Stores all running processes (applications) and the current running OS. RAM Stands for Random Access Memory

The BIOS includes boot firmware and power management. The Basic Input Output System tasks are handled by operating system drivers.

Internal Buses connect the CPU to various internal components and to expansion cards for graphics and sound.

Current

The northbridge memory controller, for RAM and PCI Express
PCI Express, for graphics cards
PCI, for other expansion cards
SATA, for disk drives

Obsolete
ATA (superseded by SATA)
AGP (superseded by PCI Express)
VLB VESA Local Bus (superseded by AGP)
ISA (expansion card slot format obsolete in PCs, but still used in industrial computers)

External Bus Controllers support ports for external peripherals. These ports may be controlled directly by the southbridge I/O controller or based on expansion cards attached to the motherboard through the PCI bus.
USB
FireWire
eSATA

Power supply
Includes power cord, switch, and cooling fan. Supplies power at appropriate voltages to the motherboard and internal disk drives. It also converts alternating current to direct current and provides different voltages to different parts of the computer.

Video display controller
Produces the output for the visual display unit. This will either be built into the motherboard or attached in its own separate slot (PCI, PCI-E, PCI-E 2.0, or AGP), in the form of a graphics card.

Removable media devices
CD (compact disc) - the most common type of removable media, suitable for music and data.

CD-ROM Drive - a device used for reading data from a CD.

CD Writer - a device used for both reading and writing da
ta to and from a CD.

DVD (digital versatile disc) - a popular type of removable media that is the same dimensions as a CD but stores up to 12 times as much information. It is the most common way of transferring digital video, and is popular for data storage.
DVD-ROM Drive - a device used for reading data from a DVD.

DVD Writer - a device used for both reading and writing data to and from a DVD.

DVD-RAM Drive - a device used for rapid writing and reading of data from a special type of DVD.

Blu-ray Disc - a high-density optical disc format for data and high-definition video. Can store 70 times as much information as a CD.

BD-ROM Drive - a device used for reading data from a Blu-ray disc.

BD Writer - a device used for both reading and writing data to and from a Blu-ray disc.

HD DVD - a discontinued competitor to the Blu-ray format.

Floppy disk - an outdated storage device consisting of a thin disk of a flexible magnetic storage medium. Used today mainly for loading RAID drivers.

Zip drive - an outdated medium-capacity removable disk storage system, first introduced by Iomega in 1994.

USB flash drive - a flash memory data storage device integrated with a USB interface, typically small, lightweight, removable, and rewritable. Capacities vary, from hundreds of megabytes (in the same ballpark as CDs) to tens of gigabytes (surpassing, at great expense, Blu-ray discs).

Tape drive - a device that reads and writes data on a magnetic tape, used for long term storage and backups.

Internal storage
Hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power.

Hard disk - for medium-term storage of data.

Solid-state drive - a device similar to hard disk, but containing no moving parts and stores data in a digital format.

RAID array controller - a device to manage several internal or external hard disks and optionally some peripherals in order to achieve performance or reliability improvement in what is called a RAID array.

Sound card
Enables the computer to output sound to audio devices, as well as accept input from a microphone. Most modern computers have sound cards built-in to the motherboard, though it is common for a user to install a separate sound card as an upgrade. Most sound cards, either built-in or added, have surround sound capabilities.

Other peripherals
In addition, hardware devices can include external components of a computer system. The following are either standard or very common.Includes various input and output devices, usually external to the computer system.

Input

Text input devices
Keyboard - a device to input text and characters by depressing buttons (referred to as keys), similar to a typewriter. The most common English-language key layout is the QWERTY layout.

Pointing devices
Mouse - a pointing device that detects two dimensional motion relative to its supporting surface.

Optical Mouse - a newer technology that uses lasers, or more commonly LEDs to track the surface under the mouse to determine motion of the mouse, to be translated into mouse movements on the screen.

Trackball - a pointing device consisting of an exposed protruding ball housed in a socket that detects rotation about two axes.

Gaming devices
Joystick - a general control device that consists of a handheld stick that pivots around one end, to detect angles in two or three dimensions.

Gamepad - a general handheld game controller that relies on the digits (especially thumbs) to provide input.

Game controller - a specific type of controller specialized for certain gaming purposes.

Image, Video input devices
Image scanner - a device that provides input by analyzing images, printed text, handwriting, or an object.

Webcam - a low resolution video camera used to provide visual input that can be easily transferred over the internet.

Audio input devices
Microphone - an acoustic sensor that provides input by converting sound into electrical signals.

Mic - converting an audio signal into electrical signal.

Output

Image, Video output devices
Printer
Monitor

Audio output devices
Speakers
Headset

24) COMPUTER ARCHITECTURE

2009-06-20T06:05:00.001-07:00

Computer architecture in computer engineering is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements and design implementations for the various parts of a computer, focusing largely on the way by which the central processing unit (CPU) performs internally and accesses addresses in memory.

It may also be defined as the science and art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals.

Overview
Computer architecture comprises at least three main subcategories:

Instruction set architecture, or ISA, is the abstract image of a computing system that is seen by a machine language (or assembly language) programmer, including the instruction set, word size, memory address modes, processor registers, and address and data formats.
Microarchitecture, also known as Computer organization is a lower level, more concrete and detailed, description of the system that involves how the constituent parts of the system are interconnected and how they interoperate in order to implement the ISA. The size of a computer's cache for instance, is an organizational issue that generally has nothing to do with the ISA.
System Design which includes all of the other hardware components within a computing system such as:

1.system interconnects such as computer buses and switches
2.memory controllers and hierarchies
3.CPU off-load mechanisms such as direct memory access
4.issues like multi-processing

Once both ISA and microarchitecture have been specified, the actual device needs to be designed into hardware. This design process is called implementation. Implementation is usually not considered architectural definition, but rather hardware design engineering.

Implementation can be further broken down into three (not fully distinct) pieces:

Logic Implementation - design of blocks defined in the microarchitecture at (primarily) the register-transfer and gate levels.
Circuit Implementation - transistor-level design of basic elements (gates, multiplexers, latches etc) as well as of some larger blocks (ALUs, caches etc) that may be implemented at this level, or even (partly) at the physical level, for performance reasons.
Physical Implementation - physical circuits are drawn out, the different circuit components are placed in a chip floor-plan or on a board and the wires connecting them are routed.
For CPUs, the entire implementation process is often called CPU design.

More specific usages of the term include more general wider-scale hardware architectures, such as cluster computing and Non-Uniform Memory Access (NUMA) architectures.

History
The term “architecture” in computer literature can be traced to the work of Lyle R. Johnson and Frederick P. Brooks, Jr., members in 1959 of the Machine Organization department in IBM’s main research center. Johnson had occasion to write a proprietary research communication about Stretch, an IBM-developed supercomputer for Los Alamos Scientific Laboratory; in attempting to characterize his chosen level of detail for discussing the luxuriously embellished computer, he noted that his description of formats, instruction types, hardware parameters, and speed enhancements aimed at the level of “system architecture” – a term that seemed more useful than “machine organization.” Subsequently Brooks, one of the Stretch designers, started Chapter 2 of a book (Planning a Computer System: Project Stretch, ed. W. Buchholz, 1962) by writing, “Computer architecture, like other architecture, is the art of determining the needs of the user of a structure and then designing to meet those needs as effectively as possible within economic and technological constraints.” Brooks went on to play a major role in the development of the IBM System/360 line of computers, where “architecture” gained currency as a noun with the definition “what the user needs to know.” Later the computer world would employ the term in many less-explicit ways.

The first mention of the term architecture in the referred computer literature is in a 1964 article describing the IBM System/360. The article defines architecture as the set of “attributes of a system as seen by the programmer, i.e., the conceptual structure and functional behavior, as distinct from the organization of the data flow and controls, the logical design, and the physical implementation.” In the definition, the programmer perspective of the computer’s functional behavior is key. The conceptual structure part of an architecture description makes the functional behavior comprehensible, and extrapolatable to a range of Use cases. Only later on did ‘internals’ such as “the way by which the CPU performs internally and accesses addresses in memory,” mentioned above, slip into the definition of computer architecture.

Sub-definitions
Some practitioners of computer architecture at companies such as Intel and AMD use more fine distinctions:

Macroarchitecture - architectural layers that are more abstract than microarchitecture, e.g. ISA
ISA (Instruction Set Architecture) - as defined above
Assembly ISA - a smart assembler may convert an abstract assembly language common to a group of machines into slightly different machine language for different implementations
Programmer Visible Macroarchitecture - higher level language tools such as compilers may define a consistent interface or contract to programmers using them, abstracting differences between underlying ISA, UISA, and microarchitectures. E.g. the C, C++, or Java standards define different Programmer Visible Macroarchitecture - although in practice the C microarchitecture for a particular computer includes
UISA (Microcode Instruction Set Architecture) - a family of machines with different hardware level microarchitectures may share a common microcode architecture, and hence a UISA.
Pin Architecture - the set of functions that a microprocessor is expected to provide, from the point of view of a hardware platform. E.g. the x86 A20M, FERR/IGNNE or FLUSH pins, and the messages that the processor is expected to emit after completing a cache invalidation so that external caches can be invalidated. Pin architecture functions are more flexible than ISA functions - external hardware can adapt to changing encodings, or changing from a pin to a message - but the functions are expected to be provided in successive implementations even if the manner of encoding them changes.

Design goals
The exact form of a computer system depends on the constraints and goals for which it was optimized. Computer architectures usually trade off standards, cost, memory capacity, latency and throughput. Sometimes other considerations, such as features, size, weight, reliability, expandability and power consumption are factors as well.

The most common scheme carefully chooses the bottleneck that most reduces the computer's speed. Ideally, the cost is allocated proportionally to assure that the data rate is nearly the same for all parts of the computer, with the most costly part being the slowest. This is how skillful commercial integrators optimize personal computers.

Performance
Computer performance is often described in terms of clock speed (usually in MHz or GHz). This refers to the cycles per second of the main clock of the CPU. However, this metric is somewhat misleading, as a machine with a higher clock rate may not necessarily have higher performance. As a result manufacturers have moved away from clock speed as a measure of performance.

Computer performance can also be measured with the amount of cache a processor has. If the speed, MHz or GHz, were to be a car then the cache is like a traffic light. No matter how fast the car goes, it still will be stopped by a red traffic light. The higher the speed, and the greater the cache, the faster a processor runs.

Modern CPUs can execute multiple instructions per clock cycle, which dramatically speeds up a program. Other factors influence speed, such as the mix of functional units, bus speeds, available memory, and the type and order of instructions in the programs being run.

There are two main types of speed, latency and throughput. Latency is the time between the start of a process and its completion. Throughput is the amount of work done per unit time. Interrupt latency is the guaranteed maximum response time of the system to an electronic event (e.g. when the disk drive finishes moving some data). Performance is affected by a very wide range of design choices — for example, pipelining a processor usually makes latency worse (slower) but makes throughput better. Computers that control machinery usually need low interrupt latencies. These computers operate in a real-time environment and fail if an operation is not completed in a specified amount of time. For example, computer-controlled anti-lock brakes must begin braking almost immediately after they have been instructed to brake.

The performance of a computer can be measured using other metrics, depending upon its application domain. A system may be CPU bound (as in numerical calculation), I/O bound (as in a webserving application) or memory bound (as in video editing). Power consumption has become important in servers and portable devices like laptops.

Benchmarking tries to take all these factors into account by measuring the time a computer takes to run through a series of test programs. Although benchmarking shows strengths, it may not help one to choose a computer. Often the measured machines split on different measures. For example, one system might handle scientific applications quickly, while another might play popular video games more smoothly. Furthermore, designers have been known to add special features to their products, whether in hardware or software, which permit a specific benchmark to execute quickly but which do not offer similar advantages to other, more general tasks.

Power consumption
Power consumption is another design criterion that factors in the design of modern computers. Power efficiency can often be traded for performance or cost benefits. With the increasing power density of modern circuits as the number of transistors per chip scales (Moore's Law), power efficiency has increased in importance. Recent processor designs such as the Intel Core 2 put more emphasis on increasing power efficiency. Also, in the world of embedded computing, power efficiency has long been and remains the primary design goal next to performance.

23) LINUX ( OPERATING SYSTEM)

2009-06-20T06:05:00.000-07:00

Linux (commonly pronounced /ˈlɪnəks/) is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed by anyone under the terms of the GNU GPL and other free licenses.

Linux is predominantly known for its use in servers, although it is installed on a wide variety of computer hardware, ranging from embedded devices and mobile phones to supercomputers. Linux distributions, installed on both desktop and laptop computers, have become increasingly commonplace in recent years, owing largely to the popular Ubuntu distribution and to the emergence of netbooks.

The name "Linux" comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The rest of the system usually comprises components such as the Apache HTTP Server, the X Window System, the K Desktop Environment, and utilities and libraries from the GNU operating system (announced in 1983 by Richard Stallman). Commonly-used applications with desktop Linux systems include the Mozilla Firefox web-browser and the OpenOffice.org office application suite. The GNU contribution is the basis for the Free Software Foundation's preferred name GNU/Linux.

History
The Unix operating system was conceived and implemented in the 1960s and first released in 1970. Its wide availability and portability meant that it was widely adopted, copied and modified by academic institutions and businesses, with its design being influential on authors of other systems.

The GNU Project, started in 1984 by Richard Stallman, had the goal of creating a "complete Unix-compatible software system" composed entirely of free software. The next year Stallman created the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has said that if the GNU kernel had been available at the time (1991), he would not have decided to write his own.

MINIX
In 1991 while attending the University of Helsinki, Torvalds began to work on a non-commercial replacement for MINIX, which would eventually become the Linux kernel.

Linux was dependent on the MINIX user space at first. With code from the GNU system freely available, it was advantageous if this could be used with the fledgling OS. Code licensed under the GNU GPL can be used in other projects, so long as they also are released under the same or a compatible license. In order to make the Linux kernel compatible with the components from the GNU Project, Torvalds initiated a switch from his original license (which prohibited commercial redistribution) to the GNU GPL. Developers worked to integrate GNU components with Linux to make a fully functional and free operating system.

Current development
Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.

For the 2.6.29 release only, the kernel's mascot, a penguin named Tux, has been temporarily replaced by Tuz in order to highlight efforts to save the Tasmanian Devil from extinction.

Design
A Linux-based system is a modular Unix-like operating system. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Such a system uses a monolithic kernel, the Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel.

Separate projects that interface with the kernel provide much of the system's higher-level functionality. The GNU userland is an important part of most Linux-based systems, providing the most common implementation of the C library, a popular shell, and many of the common Unix tools which carry out many basic operating system tasks. The graphical user interface (or GUI) used by most Linux systems is based on the X Window System.

User interface
Users can control a Linux-based system through a command line interface (or CLI), a graphical user interface (or GUI), or through controls attached to the associated hardware (this is common for embedded systems). For desktop systems, the default mode is usually graphical user interface (or GUI).

On desktop machines, KDE, GNOME and Xfce are the most popular user interfaces, though a variety of additional user interfaces exist. Most popular user interfaces run on top of the X Window System (or X), which provides network transparency, enabling a graphical application running on one machine to be displayed and controlled from another.

Other GUIs include X window managers such as FVWM, Enlightenment and Window Maker. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system.

A Linux system typically provides a CLI of some sort through a shell, which is the traditional way of interacting with a Unix system. A Linux distribution specialized for servers may use the CLI as its only interface. A “headless system” run without even a monitor can be controlled by the command line via a remote-control protocol such as SSH or telnet.

Most low-level Linux components, including the GNU Userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. A graphical terminal emulator program is often used to access the CLI from a Linux desktop.

Development
The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open source software. Linux is not the only such operating system, although it is by far the most widely used. Some free and open source software licenses are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU GPL, is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU project.

Linux based distributions are intended by developers for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX SUS, ISO and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.

Free software projects, although developed in a collaborative fashion, are often produced independently of each other. The fact that the software licenses explicitly permit redistribution, however, provides a basis for larger scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a Linux distribution.

A Linux distribution, commonly called a "distro", is a project that manages a remote collection of system software and application software packages available for download and installation through a network connection. This allows the user to adapt the operating system to his/her specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. A distribution can be installed using a CD that contains distribution-specific software for initial system installation and configuration. A package manager such as Synaptic allows later package upgrades and installs. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more generally integration of the different software packages into a coherent whole.

Programming on Linux
Most Linux distributions support dozens of programming languages. The most common collection of utilities for building both Linux applications and operating system programs is found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for Ada, C, C++, Java, and Fortran. The Linux kernel itself is written to be compiled with GCC. Proprietary compilers for Linux include the Intel C++ Compiler, Sun Studio, and IBM XL C/C++ Compiler.

Most distributions also include support for Perl, Ruby, Python and other dynamic languages. Examples of languages that are less common, but still supported, are C# via the Mono project, sponsored by Novell, and Scheme. A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM's J2SE RE, as well as many open-source projects like Kaffe.

The two main frameworks for developing graphical applications are those of GNOME and KDE. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated development environments available including Anjuta, Code::Blocks, Eclipse, KDevelop, Lazarus, MonoDevelop, NetBeans, and Omnis Studio while the long-established editors Vim and Emacs remain popular.

Uses
As well as those designed for general purpose use on desktops and servers, distributions may be specialized for different purposes including: computer architecture support, embedded systems, stability, security, localization to a specific region or language, targeting of specific user groups, support for real-time applications, or commitment to a given desktop environment. Furthermore, some distributions deliberately include only free software. Currently, over three hundred distributions are actively developed, with about a dozen distributions being most popular for general-purpose use.

Linux is a widely ported operating system kernel. The Linux kernel runs on a highly diverse range of computer architectures: in the hand-held ARM-based iPAQ and the mainframe IBM System z9, in devices ranging from mobile phones to supercomputers. Specialized distributions exist for less mainstream architectures. The ELKS kernel fork can run on Intel 8086 or Intel 80286 16-bit microprocessors, while the µClinux kernel fork may run on systems without a memory management unit. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as Macintosh computers (with both PowerPC and Intel processors), PDAs, video game consoles, portable music players, and mobile phones.

Desktop
The popularity of Linux on standard desktops (and laptops) has been increasing over the years. Currently most distributions include a graphical user environment. The two most popular such environments GNOME and KDE, both of which are mature, and support a wide variety of languages.

In the past, the performance of Linux on the desktop has been a controversial topic; for example in 2007 Con Kolivas accused the Linux community of favoring performance on servers. He quit Linux kernel development because he was frustrated with this lack of focus on the desktop, and then gave a "tell all" interview on the topic. However since then significant effort has been expended improving the desktop experience. For example, projects such as upstart aim for a faster boot time. In the field of gaming, the Linux desktop still lags behind Windows, however there are several companies that do port their own or other companies games to Linux.

Many types of applications available for Microsoft Windows and Mac OS X are also available for Linux. Commonly, either a free software application will exist which does the functions of an application found on another operating systems, or that application will, in fact, work on Linux (such as Skype). Furthermore, the Wine project provides a Windows compatibility layer to run unmodified Windows applications on Linux. CrossOver is a proprietary solution based on the open source Wine project that supports running Windows versions of Microsoft Office, Intuit applications such as Quicken and QuickBooks, Adobe Photoshop versions through CS2, and many popular games such as World of Warcraft and Team Fortress 2. In other cases, although there is no Linux port of some software in areas such as desktop publishing and professional audio, there is equivalent software available on Linux.

Many popular applications work on a wide variety of operating systems. For example Mozilla Firefox, and OpenOffice.org work on all major operating systems. Furthermore, some applications were initially developed for Linux (such as Pidgin, and GIMP) and, due to their popularity, were ported to other operating systems (including Windows and Mac OS X).

A growing number of proprietary desktop applications are also supported on Linux, see List of proprietary software for Linux. In the field of animation and visual effects, most high end software, such as AutoDesk Maya, Softimage XSI and Apple Shake, is available for Linux, Windows and/or Mac OS X.

The collaborative nature of free software development allows distributed teams to localize Linux distributions for use in locales where localizing proprietary systems would not be cost-effective. For example the Sinhalese language version of the Knoppix distribution was available significantly before Microsoft Windows XP was translated to Sinhalese. In this case the Lanka Linux User Group played a major part in developing the localized system by combining the knowledge of university professors, linguists, and local developers.

To install new software in Windows, users either download a digital distribution or use a traditional installation medium (such as CD-ROM). Both of these methods usually provide a "Software Installation Wizard" to guide the user through the setup. On most Linux distributions, there are utilities for browsing a list of thousands of applications installed with a single click. Some of these programs are the Synaptic Package Manager, PackageKit, and Yum Extender. However, installing software not in the official repositories is not always easy, and sometimes the only option is to compile from source.

Servers and supercomputers
Historically, Linux distributions have mainly been used as server operating systems, and have risen to prominence in that area; Netcraft reported in September 2006 that eight of the ten most reliable internet hosting companies ran Linux distributions on their web servers. (As of June 2008, Linux distributions represented five of ten, FreeBSD three of ten, and Microsoft two of ten)

Linux distributions are the cornerstone of the LAMP server-software combination (Linux, Apache, MySQL, Perl/PHP/Python) which has achieved popularity among developers, and which is one of the more common platforms for website hosting.

Linux distributions are also commonly used as operating systems for supercomputers: as of November 2008, out of the top 500 systems, 439 (87.8%) run a Linux distribution.

Embedded devices
Due to its low cost and ability to be easily modified, an embedded Linux is often used in embedded systems. Linux has become a major competitor to the proprietary Symbian OS found in the majority of smartphones—16.7% of smartphones sold worldwide during 2006 were using Linux—and it is an alternative to the proprietary Windows CE and Palm OS operating systems on mobile devices. Cell phones or PDAs running on Linux and built on open source platform became a trend from 2007, like Nokia N810, Openmoko's Neo1973, Motorola RAZR2 v8, Motorola ROKR E8, Motorola MING series, Motorola ZINE and the on-going Google Android. The popular TiVo digital video recorder uses a customized version of Linux. Several network firewall and router standalone products, including several from Linksys, use Linux internally, using its advanced firewall and routing capabilities. The Korg OASYS and the Yamaha Motif XS music workstations also run Linux. Furthermore, Linux is used in the leading stage lighting control system, FlyingPig/HighEnd WholeHogIII Console.

GNU/Linux
The Free Software Foundation views Linux distributions which use GNU software as GNU variants and they ask that such operating systems be referred to as GNU/Linux or a Linux-based GNU system. The media and common usage, however, refers to this family of operating systems simply as Linux, as do many large Linux distributions (e.g. Ubuntu and SuSE Linux). Some distributions use GNU/Linux (particularly notable is Debian GNU/Linux), but the term's use outside of the enthusiast community is limited. The naming issue remains a source of confusion to many newcomers, and the naming remains controversial. Linus Torvalds is against the GNU/Linux naming, stating that Linux is not a GNU project.

22) SOLARIS (OPERATING SYSTEM)

2009-06-20T05:54:00.000-07:00

Solaris is a UNIX-based operating system introduced by Sun Microsystems in 1992 as the successor to SunOS.

Solaris is known for its scalability, especially on SPARC systems, and for originating many innovative features such as DTrace and ZFS. Solaris supports SPARC-based and x86-based workstations and servers from Sun and other vendors, with efforts underway to port to additional platforms.

Solaris is certified against the Single Unix Specification. Although it was historically developed as proprietary software, it is supported on systems manufactured by all major server vendors, and the majority of its codebase is now open source software via the OpenSolaris project.

History
In 1987, AT&T and Sun announced that they were collaborating on a project to merge the most popular Unix variants on the market at that time: BSD, System V, and Xenix. This would become Unix System V Release 4 (SVR4).

On September 4, 1991, Sun announced that it would replace its existing BSD-derived Unix, SunOS 4, with one based on SVR4. This was identified internally as SunOS 5, but a new marketing name was introduced at the same time: Solaris 2. While SunOS 4.1.x micro releases were retroactively named Solaris 1 by Sun, the Solaris name is almost exclusively used to refer to the SVR4-derived SunOS 5.0 and later.

The justification for this new "overbrand" was that it encompassed not only SunOS, but also the OpenWindows graphical user interface and Open Network Computing (ONC) functionality. The SunOS minor version is included in the Solaris release number; for example, Solaris 2.4 incorporated SunOS 5.4. After Solaris 2.6, Sun dropped the "2." from the number, so Solaris 7 incorporates SunOS 5.7, and the latest release SunOS 5.10 forms the core of Solaris 10.

Supported architectures
Solaris uses a common code base for the platforms it supports: SPARC and i86pc (which includes both x86 and x86-64).

Solaris has a reputation for being well-suited to symmetric multiprocessing, supporting a large number of CPUs. It has historically been tightly integrated with Sun's SPARC hardware (including support for 64-bit SPARC applications since Solaris 7), with which it is marketed as a combined package. This has often led to more reliable systems, but at a cost premium over commodity PC hardware. However, it has also supported x86 systems since Solaris 2.1 and the latest version, Solaris 10, includes support for 64-bit x86 applications, allowing Sun to capitalize on the availability of commodity 64-bit CPUs based on the x86-64 architecture. Sun has heavily marketed Solaris for use with both its own "x64" workstations and servers based on AMD Opteron and Intel Xeon processors, as well as x86 systems manufactured by companies such as Dell, Hewlett-Packard, and IBM. As of 2009, the following vendors support Solaris for their x86 server systems:

Dell - will "test, certify, and optimize Solaris and OpenSolaris on its rack and blade servers and offer them as one of several choices in the overall Dell software menu"

IBM - also distributes Solaris and Solaris Subscriptions for select x86-based IBM System x servers and BladeCenter servers

Intel

Hewlett-Packard - distributes and provides software technical support for Solaris on ProLiant server and blade systems

Fujitsu Siemens.

Other platforms
Solaris 2.5.1 included support for the PowerPC platform (PowerPC Reference Platform), but the port was canceled before the Solaris 2.6 release. In January 2006 a community of developers at Blastwave began work on a PowerPC port which they named Polaris. In October 2006, an OpenSolaris community project based on the Blastwave efforts and Sun Labs' Project Pulsar, which re-integrated the relevant parts from Solaris 2.5.1 into OpenSolaris, announced its first official source code release.

A port of Solaris to the Intel Itanium architecture was announced in 1997 but never brought to market.

On November 28, 2007, IBM, Sun, and Sine Nomine Associates demonstrated a preview of OpenSolaris for System z running on an IBM System z mainframe under z/VM, called Sirius (in analogy to the Polaris project, and also due to the primary developer's Australian nationality: HMS Sirius of 1786 was a ship of the First Fleet to Australia). On October 17, 2008 a prototype release of Sirius was made available and on November 19 the same year, IBM authorized the use of Sirius on System z IFL processors.

Solaris also supports the Linux platform ABI, allowing Solaris to run native Linux binaries on x86 systems. This feature is called "Solaris Containers for Linux Applications" or SCLA, based on the branded zones functionality introduced in Solaris 10 8/07.

Usage with installation
Solaris can be installed from physical media or a network for use on a desktop or server.

Solaris can be interactively installed from a text console on platforms without a video display and mouse. This may be selected for servers, in a rack, in a remote data center, from a terminal server or even dial up modem.

Solaris can be interactively installed from a graphical console. This may be selected for personal workstations or laptops, in a local area, where a console may normally be used.

Solaris can be automatically installed over a network. System administrators can customize installations with scripts and configuration files, including configuration and automatic installation of third-party software, without purchasing additional software management utilities.

When Solaris is installed, the operating system will reside on the same system where the installation occurred. Applications may be individually installed on the local system, or can be mounted via the network from a remote system.

Usage without installation
Solaris can be used without separately installing the operating system on a desktop or server.

Solaris can be booted from a remote server providing an OS image in a diskless environment, or in an environment where an internal disk is only used for swap space. In this configuration, the operating system still runs locally on the system. Applications may or may not reside locally when they are running. This may be selected for businesses or educational institutions where rapid setup is required (workstations can be "rolled off" of a loading dock, the MAC address registered into a central server, the workstation plugged in, and users can immediately leverage the desktop) or rapid replacement is required (if a desktop hardware failure occurs, a new workstation is pulled from a closet, plugged in, and a user can resume their work from their last saved point.)

Solaris can be used from an X terminal, which can boot from embedded or network accessible firmware and display a desktop immediately to the user. Applications and the operating system run remotely on one or more servers, but the graphical rendering (and occasionally the window manager) is offloaded to the X terminal. In the case of a desktop hardware failure, an X terminal can be easily replaced, and a user can resume their work from their last saved point.

Solaris can also be used from a thin client. Applications, operating system, window manager, and graphical rendering runs on one or more remote servers. Administrators can add a user account to a central Solaris system and a thin client can be rolled from a closet, placed on a desktop, and a user can start work immediately. If there is a hardware failure, the thin client can be swapped and the user can resume their work from the exact point of failure, whether or not the work was saved.

Desktop environments
Early releases of Solaris used OpenWindows as the standard desktop environment. In Solaris 2.0 to 2.2, OpenWindows supported both NeWS and X applications, and provided backward compatibility for SunView applications from Sun's older desktop environment. NeWS allowed applications to be built in an object oriented way using PostScript, a common printing language released in 1982. The X Window System originated from MIT's Project Athena in 1984 and allowed for the display of an application to be disconnected from the machine where the application was running, separated by a network connection. Sun’s original bundled SunView application suite was ported to X.

Sun later dropped support for legacy SunView applications and NeWS with OpenWindows 3.3, which shipped with Solaris 2.3, and switched to X11R5 with Display Postscript support. The graphical look and feel remained based upon OPEN LOOK. OpenWindows 3.6.2 was the last release under Solaris 8. The OPEN LOOK Window Manager (olwm) with other OPEN LOOK specific applications were dropped in Solaris 9, but support libraries were still bundled, providing long term binary backwards compatibility with existing applications. The OPEN LOOK Virtual Window Manager (olvwm) can still be downloaded for Solaris from sunfreeware and works on releases as recent as Solaris 10.
Sun and other Unix vendors created an industry alliance to standardize Unix desktops. As a member of COSE, the Common Open Software Environment initiative, Sun helped co-develop the Common Desktop Environment. CDE was an initiative to create a standard Unix desktop environment. Each vendor contributed different components: Hewlett-Packard contributed the window manager, IBM provided the file manager, and Sun provided the e-mail and calendar facilities as well as drag-and-drop support (ToolTalk). This new desktop environment was based upon the Motif look and feel and the old OPEN LOOK desktop environment was considered legacy. Solaris 2.5 onwards supported CDE. CDE unified Unix desktops across multiple open system vendors.

In 2001, Sun issued a preview release of the open-source desktop environment GNOME 1.4, based on the GTK+ toolkit, for Solaris 8. Solaris 9 8/03 introduced GNOME 2.0 as an alternative to CDE. Solaris 10 includes Sun's Java Desktop System, which is based on GNOME and comes with a large set of applications, including StarOffice, Sun's office suite. Sun describes JDS as a "major component" of Solaris 10.

The open source desktop environments KDE and XFCE, along with numerous other window managers, also compile and run on recent versions of Solaris.

Sun was investing in a new desktop environment called Project Looking Glass since 2003. The environment has been copied by other desktop vendors.

License
Solaris' source code (with a few exceptions) has been released under the Common Development and Distribution License (CDDL) via the OpenSolaris project. The CDDL is an OSI-approved license. It is considered by the Free Software Foundation to be free but the GPL is incompatible with it.

OpenSolaris was seeded on June 14, 2005 from the then-current Solaris development code base; both binary and source versions are currently downloadable and licensed without cost. Source for upcoming features such as Xen support is now added to the OpenSolaris project as a matter of course, and Sun has said that future releases of Solaris proper will henceforth be derived from OpenSolaris.

21) PROGRAMMING LANGUAGE "JAVA"

2009-06-20T05:38:00.000-07:00

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode (class file) that can run on any Java virtual machine (JVM) regardless of computer architecture.

The original and reference implementation Java compilers, virtual machines, and class libraries were developed by Sun from 1995. As of May 2007, in compliance with the specifications of the Java Community Process, Sun made available most of their Java technologies as free software under the GNU General Public License. Others have also developed alternative implementations of these Sun technologies, such as the GNU Compiler for Java and GNU Classpath.

History
James Gosling initiated the Java language project in June 1991 for use in one of his many set-top box projects.[5] The language, initially called Oak after an oak tree that stood outside Gosling's office, also went by the name Green and ended up later renamed as Java, from a list of random words. Gosling aimed to implement a virtual machine and a language that had a familiar C/C++ style of notation.

Sun released the first public implementation as Java 1.0 in 1995. It promised "Write Once, Run Anywhere" (WORA), providing no-cost run-times on popular platforms. Fairly secure and featuring configurable security, it allowed network- and file-access restrictions. Major web browsers soon incorporated the ability to run Java applets within web pages, and Java quickly became popular. With the advent of Java 2 (released initially as J2SE 1.2 in December 1998), new versions had multiple configurations built for different types of platforms. For example, J2EE targeted enterprise applications and the greatly stripped-down version J2ME for mobile applications. J2SE designated the Standard Edition. In 2006, for marketing purposes, Sun renamed new J2 versions as Java EE, Java ME, and Java SE, respectively.

In 1997, Sun Microsystems approached the ISO/IEC JTC1 standards body and later the Ecma International to formalize Java, but it soon withdrew from the process. Java remains a de facto standard, controlled through the Java Community Process. At one time, Sun made most of its Java implementations available without charge, despite their proprietary software status. Sun generated revenue from Java through the selling of licenses for specialized products such as the Java Enterprise System. Sun distinguishes between its Software Development Kit (SDK) and Runtime Environment (JRE) (a subset of the SDK); the primary distinction involves the JRE's lack of the compiler, utility programs, and header files.

On 13 November 2006, Sun released much of Java as free and open source software under the terms of the GNU General Public License (GPL). On 8 May 2007 Sun finished the process, making all of Java's core code available under free software / open-source distribution terms, aside from a small portion of code to which Sun did not hold the copyright.

Philosophy
There were five primary goals in the creation of the Java language:

1.It should be "simple, object oriented, and familiar".
2.It should be "robust and secure".
3.It should be "architecture neutral and portable".
4.It should execute with "high performance".
5.It should be "interpreted, threaded, and dynamic".

Java Platform
One characteristic of Java is portability, which means that computer programs written in the Java language must run similarly on any supported hardware/operating-system platform. One should be able to write a program once, compile it once, and run it anywhere.

This is achieved by compiling the Java language code, not to machine code but to Java bytecode – instructions analogous to machine code but intended to be interpreted by a virtual machine (VM) written specifically for the host hardware. End-users commonly use a Java Runtime Environment (JRE) installed on their own machine for standalone Java applications, or in a Web browser for Java applets.

Standardized libraries provide a generic way to access host specific features such as graphics, threading and networking. In some JVM versions, bytecode can be compiled to native code, either before or during program execution, resulting in faster execution.

A major benefit of using bytecode is porting. However, the overhead of interpretation means that interpreted programs almost always run more slowly than programs compiled to native executables would, and Java suffered a reputation for poor performance. This gap has been narrowed by a number of optimization techniques introduced in the more recent JVM implementations.

One such technique, known as just-in-time (JIT) compilation, translates Java bytecode into native code the first time that code is executed, then caches it. This results in a program that starts and executes faster than pure interpreted code can, at the cost of introducing occasional compilation overhead during execution. More sophisticated VMs also use dynamic recompilation, in which the VM analyzes the behavior of the running program and selectively recompiles and optimizes parts of the program. Dynamic recompilation can achieve optimizations superior to static compilation because the dynamic compiler can base optimizations on knowledge about the runtime environment and the set of loaded classes, and can identify hot spots - parts of the program, often inner loops, that take up the most execution time. JIT compilation and dynamic recompilation allow Java programs to approach the speed of native code without losing portability.

Another technique, commonly known as static compilation, or ahead-of-time (AOT) compilation, is to compile directly into native code like a more traditional compiler. Static Java compilers translate the Java source or bytecode to native object code. This achieves good performance compared to interpretation, at the expense of portability; the output of these compilers can only be run on a single architecture. AOT could give Java something close to native performance, yet it is still not portable since there are no compiler directives, and all the pointers are indirect with no way to micro manage garbage collection.

Java's performance has improved substantially since the early versions, and performance of JIT compilers relative to native compilers has in some tests been shown to be quite similar. The performance of the compilers does not necessarily indicate the performance of the compiled code; only careful testing can reveal the true performance issues in any system.

One of the unique advantages of the concept of a runtime engine is that even the most serious errors (exceptions) in a Java program should not 'crash' the system under any circumstances, provided the JVM itself is properly implemented. Moreover, in runtime engine environments such as Java there exist tools that attach to the runtime engine and every time that an exception of interest occurs they record debugging information that existed in memory at the time the exception was thrown (stack and heap values). These Automated Exception Handling tools provide 'root-cause' information for exceptions in Java programs that run in production, testing or development environments. Such precise debugging is much more difficult to implement without the run-time support that the JVM offers.

Implementations
Sun Microsystems officially licenses the Java Standard Edition platform for Microsoft Windows, Linux, Mac OS X, and Solaris. Through a network of third-party vendors and licensees, alternative Java environments are available for these and other platforms.

Sun's trademark license for usage of the Java brand insists that all implementations be "compatible". This resulted in a legal dispute with Microsoft after Sun claimed that the Microsoft implementation did not support RMI or JNI and had added platform-specific features of their own. Sun sued in 1997, and in 2001 won a settlement of $20 million as well as a court order enforcing the terms of the license from Sun. As a result, Microsoft no longer ships Java with Windows, and in recent versions of Windows, Internet Explorer cannot support Java applets without a third-party plugin. Sun, and others, have made available free Java run-time systems for those and other versions of Windows.

Platform-independent Java is essential to the Java EE strategy, and an even more rigorous validation is required to certify an implementation. This environment enables portable server-side applications, such as Web services, servlets, and Enterprise JavaBeans, as well as with embedded systems based on OSGi, using Embedded Java environments. Through the new GlassFish project, Sun is working to create a fully functional, unified open-source implementation of the Java EE technologies.

Sun also distributes a superset of the JRE called the Java Development Kit (commonly known as the JDK), which includes development tools such as the Java compiler, Javadoc, Jar and debugger.

Automatic memory management
Java uses an automatic garbage collector to manage memory in the object lifecycle. The programmer determines when objects are created, and the Java runtime is responsible for recovering the memory once objects are no longer in use. Once no references to an object remain, the unreachable object becomes eligible to be freed automatically by the garbage collector. Something similar to a memory leak may still occur if a programmer's code holds a reference to an object that is no longer needed, typically when objects that are no longer needed are stored in containers that are still in use. If methods for a nonexistent object are called, a "null pointer exception" is thrown.

One of the ideas behind Java's automatic memory management model is that programmers be spared the burden of having to perform manual memory management. In some languages memory for the creation of objects is implicitly allocated on the stack, or explicitly allocated and deallocated from the heap. Either way the responsibility of managing memory resides with the programmer. If the program does not deallocate an object, a memory leak occurs. If the program attempts to access or deallocate memory that has already been deallocated, the result is undefined and difficult to predict, and the program is likely to become unstable and/or crash. This can be partially remedied by the use of smart pointers, but these add overhead and complexity.

Garbage collection may happen at any time. Ideally, it will occur when a program is idle. It is guaranteed to be triggered if there is insufficient free memory on the heap to allocate a new object; this can cause a program to stall momentarily. Where performance or response time is important, explicit memory management and object pools are often used.

Java does not support C/C++ style pointer arithmetic, where object addresses and unsigned integers (usually long integers) can be used interchangeably. This allows the garbage collector to relocate referenced objects, and ensures type safety and security.

As in C++ and some other object-oriented languages, variables of Java's primitive types are not objects. Values of primitive types are either stored directly in fields (for objects) or on the stack (for methods) rather than on the heap, as commonly true for objects (but see Escape analysis). This was a conscious decision by Java's designers for performance reasons. Because of this, Java was not considered to be a pure object-oriented programming language. However, as of Java 5.0, autoboxing enables programmers to proceed as if primitive types are instances of their wrapper classes.

Syntax
The syntax of Java is largely derived from C++. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object oriented language. All code is written inside a class and everything is an object, with the exception of the intrinsic data types (ordinal and real numbers, boolean values, and characters), which are not classes for performance reasons.

Java suppresses several features (such as operator overloading and multiple inheritance) for classes in order to simplify the language and to prevent possible errors and anti-pattern design.

Java uses the same commenting methods as C++. There are two different styles of comment: a single line style marked with two forward slashes, and a multiple line style opened with a forward slash asterisk (/*) and closed with an asterisk forward slash (*/).

Example:

//This is an example of a single line comment using two forward slashes

/* This is an example of a multiple line comment using the forward slash
and asterisk. This type of comment can be used to hold a lot of information
but it is very important to remember to close the comment. */

Examples

Hello world

The traditional Hello world program can be written in Java as:

/*
* Outputs "Hello, world!" and then exits
*/

public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, world!");
}

}

By convention, source files are named after the public class they contain, appending the suffix .java, for example, HelloWorld.java. It must first be compiled into bytecode, using a Java compiler, producing a file named HelloWorld.class. Only then can it be executed, or 'launched'. The java source file may only contain one public class but can contain multiple classes with less than public access and any number of public inner classes.

A class that is declared private may be stored in any .java file. The compiler will generate a class file for each class defined in the source file. The name of the class file is the name of the class, with .class appended. For class file generation, anonymous classes are treated as if their name was the concatenation of the name of their enclosing class, a $, and an integer.

The keyword public denotes that a method can be called from code in other classes, or that a class may be used by classes outside the class hierarchy. The class hierarchy is related to the name of the directory in which the .java file is.

The keyword static in front of a method indicates a static method, which is associated only with the class and not with any specific instance of that class. Only static methods can be invoked without a reference to an object. Static methods cannot access any method variables that are not static.

The keyword void indicates that the main method does not return any value to the caller. If a Java program is to exit with an error code, it must call System.exit() explicitly.

The method name "main" is not a keyword in the Java language. It is simply the name of the method the Java launcher calls to pass control to the program. Java classes that run in managed environments such as applets and Enterprise Java Beans do not use or need a main() method. A java program may contain multiple classes that have main methods, which means that the VM needs to be explicitly told which class to launch from.

The main method must accept an array of String objects. By convention, it is referenced as args although any other legal identifier name can be used. Since Java 5, the main method can also use variable arguments, in the form of public static void main(String... args), allowing the main method to be invoked with an arbitrary number of String arguments. The effect of this alternate declaration is semantically identical (the args parameter is still an array of String objects), but allows an alternate syntax for creating and passing the array.

The Java launcher launches Java by loading a given class (specified on the command line or as an attribute in a JAR) and starting its public static void main(String[]) method. Stand-alone programs must declare this method explicitly. The String[] args parameter is an array of String objects containing any arguments passed to the class. The parameters to main are often passed by means of a command line.

Printing is part of a Java standard library: The System class defines a public static field called out. The out object is an instance of the PrintStream class and provides many methods for printing data to standard out, including println(String) which also appends a new line to the passed string.

The string "Hello world!" is automatically converted to a String object by the compiler.

A more comprehensive example

// OddEven.java
import javax.swing.JOptionPane;

public class OddEven {
// "input" is the number that the user gives to the computer
private int input; // a whole number("int" means integer)

/*
* This is the constructor method. It gets called when an object of the OddEven type
* is being created.
*/
public OddEven() {
//Code not shown
}

// This is the main method. It gets called when this class is run through a Java interpreter.
public static void main(String[] args) {
/*
* This line of code creates a new instance of this class called "number" (also known as an
* Object) and initializes it by calling the constructor. The next line of code calls
* the "showDialog()" method, which brings up a prompt to ask you for a number
*/
OddEven number = new OddEven();
number.showDialog();
}

public void showDialog() {
/*
* "try" makes sure nothing goes wrong. If something does,
* the interpreter skips to "catch" to see what it should do.
*/
try {
/*
* The code below brings up a JOptionPane, which is a dialog box
* The String returned by the "showInputDialog()" method is converted into
* an integer, making the program treat it as a number instead of a word.
* After that, this method calls a second method, calculate() that will
* display either "Even" or "Odd."
*/
input = new Integer(JOptionPane.showInputDialog("Please Enter A Number"));
calculate();
} catch (NumberFormatException e) {
/*
* Getting in the catch block means that there was a problem with the format of
* the number. Probably some letters were typed in instead of a number.
*/
System.err.println("ERROR: Invalid input. Please type in a numerical value.");
}
}

/*
* When this gets called, it sends a message to the interpreter.
* The interpreter usually shows it on the command prompt (For Windows users)
* or the terminal (For Linux users).(Assuming it's open)
*/
private void calculate() {
if (input % 2 == 0) {
System.out.println("Even");
} else {
System.out.println("Odd");
}
}
}
The import statement imports the JOptionPane class from the javax.swing package.
The OddEven class declares a single private field of type int named input. Every instance of the OddEven class has its own copy of the input field. The private declaration means that no other class can access (read or write) the input field.
OddEven() is a public constructor. Constructors have the same name as the enclosing class they are declared in, and unlike a method, have no return type. A constructor is used to initialize an object that is a newly created instance of the class.
The dialog returns a String that is converted to an int by the Integer.parseInt(String) method.
The calculate() method is declared without the static keyword. This means that the method is invoked using a specific instance of the OddEven class. (The reference used to invoke the method is passed as an undeclared parameter of type OddEven named this.) The method tests the expression input % 2 == 0 using the if keyword to see if the remainder of dividing the input field belonging to the instance of the class by two is zero. If this expression is true, then it prints Even; if this expression is false it prints Odd. (The input field can be equivalently accessed as this.input, which explicitly uses the undeclared this parameter.)
OddEven number = new OddEven(); declares a local object reference variable in the main method named number. This variable can hold a reference to an object of type OddEven. The declaration initializes number by first creating an instance of the OddEven class, using the new keyword and the OddEven() constructor, and then assigning this instance to the variable.
The statement number.showDialog(); calls the calculate method. The instance of OddEven object referenced by the number local variable is used to invoke the method and passed as the undeclared this parameter to the calculate method.
input = new Integer(JOptionPane.showInputDialog("Please Enter A Number")); is a statement that converts the type of String to the primitive type int by taking advantage of the wrapper class Integer.

Special classes

Applet

Java applets are programs that are embedded in other applications, typically in a Web page displayed in a Web browser.

// Hello.java
import javax.swing.JApplet;
import java.awt.Graphics;

public class Hello extends JApplet {
public void paintComponent(Graphics g) {
g.drawString("Hello, world!", 65, 95);
}
}
The import statements direct the Java compiler to include the javax.swing.JApplet and java.awt.Graphics classes in the compilation. The import statement allows these classes to be referenced in the source code using the simple class name (i.e. JApplet) instead of the fully qualified class name (i.e. javax.swing.JApplet).

The Hello class extends (subclasses) the JApplet (Java Applet) class; the JApplet class provides the framework for the host application to display and control the lifecycle of the applet. The JApplet class is a JComponent (Java Graphical Component) which provides the applet with the capability to display a graphical user interface (GUI) and respond to user events.

The Hello class overrides the paintComponent(Graphics) method inherited from the Container superclass to provide the code to display the applet. The paint() method is passed a Graphics object that contains the graphic context used to display the applet. The paintComponent() method calls the graphic context drawString(String, int, int) method to display the "Hello, world!" string at a pixel offset of (65, 95) from the upper-left corner in the applet's display.

An applet is placed in an HTML document using the HTML element. The applet tag has three attributes set: code="Hello" specifies the name of the JApplet class and width="200" height="200" sets the pixel width and height of the applet. Applets may also be embedded in HTML using either the object or embed element, although support for these elements by Web browsers is inconsistent. However, the applet tag is deprecated, so the object tag is preferred where supported.

The host application, typically a Web browser, instantiates the Hello applet and creates an AppletContext for the applet. Once the applet has initialized itself, it is added to the AWT display hierarchy. The paint method is called by the AWT event dispatching thread whenever the display needs the applet to draw itself.

Generics
In 2004 generics were added to the Java language, as part of J2SE 5.0. Prior to the introduction of generics, each variable declaration had to be of a specific type. For container classes, for example, this is a problem because there is no easy way to create a container that accepts only specific types of objects. Either the container operates on all subtypes of a class or interface, usually Object, or a different container class has to be created for each contained class. Generics allow compile-time type checking without having to create a large number of container classes, each containing almost identical code.

Class libraries
Java libraries are the compiled byte codes of source code developed by the JRE implementor to support application development in Java. Examples of these libraries are:

The core libraries, which include:

Collection libraries that implement data structures such as lists, dictionaries, trees and sets

XML Processing (Parsing, Transforming, Validating) libraries
Security

Internationalization and localization libraries

The integration libraries, which allow the application writer to communicate with external systems. These libraries include:

The Java Database Connectivity (JDBC) API for database access

Java Naming and Directory Interface (JNDI) for lookup and discovery

RMI and CORBA for distributed application development

JMX for managing and monitoring applications

User Interface libraries, which include:

The (heavyweight, or native) Abstract Window Toolkit (AWT), which provides GUI components, the means for laying out those components and the means for handling events from those components

The (lightweight) Swing libraries, which are built on AWT but provide (non-native) implementations of the AWT widgetry

APIs for audio capture, processing, and playback

A platform dependent implementation of Java virtual machine (JVM) that is the means by which the byte codes of the Java libraries and third party applications are executed

Plugins, which enable applets to be run in Web browsers

Java Web Start, which allows Java applications to be efficiently distributed to end users across the Internet

Licensing and documentation.

20) PROGRAMMING LANGUAGE "C++"

2009-06-20T05:28:00.000-07:00

C++ (read as "C Plus Plus") is a general-purpose programming language. It is regarded as a middle-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell Labs as an enhancement to the C programming language and originally named "C with Classes". It was renamed to C++ in 1983.

C++ is widely used in the software industry. Some of its application domains include systems software, application software, device drivers, embedded software, high-performance server and client applications, and entertainment software such as video games. Several groups provide both free and proprietary C++ compiler software, including the GNU Project, Microsoft, Intel, Borland and others.

The language began as enhancements to C, first adding classes, then virtual functions, operator overloading, multiple inheritance, templates, and exception handling among other features. After years of development, the C++ programming language standard was ratified in 1998 as ISO/IEC 14882:1998. That standard is still current, but is amended by the 2003 technical corrigendum, ISO/IEC 14882:2003. The next standard version (known informally as C++0x) is in development.

C++ is a statically typed, free-form, multi-paradigm, compiled language where compilation creates machine code for a target machine hardware.

History

Stroustrup began work on 'C with Classes' in 1979. The idea of creating a new language originated from Stroustrup's experience in programming for his Ph.D. thesis. Stroustrup found that Simula had features that were very helpful for large software development, but the language was too slow for practical use, while BCPL was fast but too low-level to be suitable for large software development. When Stroustrup started working in AT&T Bell Labs, he had the problem of analyzing the UNIX kernel with respect to distributed computing. Remembering his Ph.D. experience, Stroustrup set out to enhance the C language with Simula-like features. C was chosen because it was general-purpose, fast, portable and widely used. Besides C and Simula, some other languages that inspired him were ALGOL 68, Ada, CLU and ML. At first, the class, derived class, strong type checking, inlining, and default argument features were added to C via Cfront. The first commercial release occurred in October 1985.

In 1983, the name of the language was changed from C with Classes to C++ (++ being the increment operator in C and C++). New features were added including virtual functions, function name and operator overloading, references, constants, user-controlled free-store memory control, improved type checking, and BCPL style single-line comments with two forward slashes (//). In 1985, the first edition of The C++ Programming Language was released, providing an important reference to the language, since there was not yet an official standard. In 1989, Release 2.0 of C++ was released. New features included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for the future standard. Late addition of features included templates, exceptions, namespaces, new casts, and a Boolean type.

As the C++ language evolved, a standard library also evolved with it. The first addition to the C++ standard library was the stream I/O library which provided facilities to replace the traditional C functions such as printf and scanf. Later, among the most significant additions to the standard library, was the Standard Template Library.

C++ continues to be used and is still one of the preferred programming languages to develop professional applications. The language has gone from being mostly Western to attracting programmers from all over the world.

Etymology
According to Stroustrup: "the name signifies the evolutionary nature of the changes from C". During C++'s development period, the language had been referred to as "new C", then "C with Classes". The final name is credited to Rick Mascitti (mid-1983) and was first used in December 1983. When Mascitti was questioned informally in 1992 about the naming, he indicated that it was given in a tongue-in-cheek spirit. It stems from C's "++" operator (which increments the value of a variable) and a common naming convention of using "+" to indicate an enhanced computer program. There is no language called "C plus". ABCL/c+ was the name of an earlier, unrelated programming language.

Philosophy
In The Design and Evolution of C++ (1994), Bjarne Stroustrup describes some rules that he uses for the design of C++:

C++ is designed to be a statically typed, general-purpose language that is as efficient and portable as C.

C++ is designed to directly and comprehensively support multiple programming styles (procedural programming, data abstraction, object-oriented programming, and generic programming).

C++ is designed to give the programmer choice, even if this makes it possible for the programmer to choose incorrectly.

C++ is designed to be as compatible with C as possible, therefore providing a smooth transition from C.

C++ avoids features that are platform specific or not general purpose.

C++ does not incur overhead for features that are not used (the "zero-overhead principle").

C++ is designed to function without a sophisticated programming environment.

Inside the C++ Object Model (Lippman, 1996) describes how compilers may convert C++ program statements into an in-memory layout. Compiler authors are, however, free to implement the standard in their own manner.

Standard library
The 1998 ANSI/ISO C++ standard consists of two parts: the core language and the C++ standard library; the latter includes most of the Standard Template Library (STL) and a slightly modified version of the C standard library. Many C++ libraries exist which are not part of the standard, and, using linkage specification, libraries can even be written in languages such as C, Fortran, Pascal, or BASIC. Which of these are supported is compiler dependent.

The C++ standard library incorporates the C standard library with some small modifications to make it optimized with the C++ language. Another large part of the C++ library is based on the STL. This provides such useful tools as containers (for example vectors and lists), iterators to provide these containers with array-like access and algorithms to perform operations such as searching and sorting. Furthermore (multi)maps (associative arrays) and (multi)sets are provided, all of which export compatible interfaces. Therefore it is possible, using templates, to write generic algorithms that work with any container or on any sequence defined by iterators. As in C, the features of the library are accessed by using the #include directive to include a standard header. C++ provides 69 standard headers, of which 19 are deprecated.

The STL was originally a third-party library from HP and later SGI, before its incorporation into the C++ standard. The standard does not refer to it as "STL", as it is merely a part of the standard library, but many people still use that term to distinguish it from the rest of the library (input/output streams, internationalization, diagnostics, the C library subset, etc.).

Most C++ compilers provide an implementation of the C++ standard library, including the STL. Compiler-independent implementations of the STL, such as STLPort, also exist. Other projects also produce various custom implementations of the C++ standard library and the STL with various design goals.

Language features
C++ inherits most of C's syntax and the C preprocessor. The following is a Hello world program which uses the C++ standard library stream facility to write a message to standard output:

#include

int main()
{
std::cout << "Hello, world!\n";
}

Operators and operator overloading
C++ provides more than 30 operators, covering basic arithmetic, bit manipulation, indirection, comparisons, logical operations and more. Almost all operators can be overloaded for user-defined types, with a few notable exceptions such as member access (. and .*). The rich set of overloadable operators is central to using C++ as a domain specific language. The overloadable operators are also an essential part of many advanced C++ programming techniques, such as smart pointers. Overloading an operator does not change the precedence of calculations involving the operator, nor does it change the number of operands that the operator uses (any operand may however be ignored).

Templates
C++ templates enable generic programming. C++ supports both function and class templates. Templates may be parameterized by types, compile-time constants, and other templates. C++ templates are implemented by instantiation at compile-time. To instantiate a template, compilers substitute specific arguments for a template's parameters to generate a concrete function or class instance. Templates are a powerful tool that can be used for generic programming, template metaprogramming, and code optimization, but this power implies a cost. Template use may increase code size, since each template instantiation produces a copy of the template code: one for each set of template arguments. This is in contrast to run-time generics seen in other languages (e.g. Java) where at compile-time the type is erased and a single template body is preserved.

Templates are different from macros: while both of these compile-time language features enable conditional compilation, templates are not restricted to lexical substitution. Templates are aware of the semantics and type system of their companion language, as well as all compile-time type definitions, and can perform high-level operations including programmatic flow control based on evaluation of strictly type-checked parameters. Macros are capable of conditional control over compilation based on predetermined criteria, but cannot instantiate new types, recurse, or perform type evaluation and in effect are limited to pre-compilation text-substitution and text-inclusion/exclusion. In other words, macros can control compilation flow based on pre-defined symbols but cannot, unlike templates, independently instantiate new symbols. Templates are a tool for static polymorphism (see below) and generic programming.

In addition, templates are a compile time mechanism in C++ which is Turing-complete, meaning that any computation expressible by a computer program can be computed, in some form, by a template metaprogram prior to runtime.

In summary, a template is a compile-time parameterized function or class written without knowledge of the specific arguments used to instantiate it. After instantiation the resulting code is equivalent to code written specifically for the passed arguments. In this manner, templates provide a way to decouple generic, broadly-applicable aspects of functions and classes (encoded in templates) from specific aspects (encoded in template parameters) without sacrificing performance due to abstraction.

Objects
C++ introduces object-oriented (OO) features to C. It offers classes, which provide the four features commonly present in OO (and some non-OO) languages: abstraction, encapsulation, inheritance, and polymorphism. Objects are instances of classes created at runtime. The class can be thought of as a template from which many different individual objects may be generated as a program runs.

Inheritance
Inheritance allows one data type to acquire properties of other data types. Inheritance from a base class may be declared as public, protected, or private. This access specifier determines whether unrelated and derived classes can access the inherited public and protected members of the base class. Only public inheritance corresponds to what is usually meant by "inheritance". The other two forms are much less frequently used. If the access specifier is omitted, a "class" inherits privately, while a "struct" inherits publicly. Base classes may be declared as virtual; this is called virtual inheritance. Virtual inheritance ensures that only one instance of a base class exists in the inheritance graph, avoiding some of the ambiguity problems of multiple inheritance.

Multiple inheritance is a C++ feature sometimes considered controversial. Multiple inheritance allows a class to be derived from more than one base class; this can result in a complicated graph of inheritance relationships. For example, a "Flying Cat" class can inherit from both "Cat" and "Flying Mammal". Some other languages, such as Java or C#, accomplish something similar (although more limited) by allowing inheritance of multiple interfaces while restricting the number of base classes to one (interfaces, unlike classes, provide only declarations of member functions, no implementation or member data). Interfaces and abstract classes in Java and C# can be expressed in C++ as a class containing only function declarations, often known as an abstract base class or "ABC." Programmers preferring the Java/C# model of inheritance can choose to inherit only one non-abstract class, and can otherwise limit themselves to only abstract classes.

Polymorphism
Polymorphism enables one common interface for many implementations, and for objects to act differently under different circumstances.

C++ supports several kinds of static (compile-time) and dynamic (run-time) polymorphisms. Compile-time polymorphism does not allow for certain run-time decisions, while run-time polymorphism typically incurs a performance penalty.

Static polymorphism
Function overloading allows programs to declare multiple functions having the same name (but with different arguments). The functions are distinguished by the number and/or types of their formal parameters. Thus, the same function name can refer to different functions depending on the context in which it is used. The type returned by the function is not used to distinguish overloaded functions.

When declaring a function, a programmer can specify default arguments for one or more parameters. Doing so allows the parameters with defaults to optionally be omitted when the function is called, in which case the default arguments will be used. When a function is called with fewer arguments than there are declared parameters, explicit arguments are matched to parameters in left-to-right order, with any unmatched parameters at the end of the parameter list being assigned their default arguments. In many cases, specifying default arguments in a single function declaration is preferable to providing overloaded function definitions with different numbers of parameters.

Templates in C++ provide a sophisticated mechanism for writing generic, polymorphic code. In particular, through the Curiously Recurring Template Pattern it's possible to implement a form of static polymorphism that closely mimics the syntax for overriding virtual functions. Since C++ templates are type-aware and Turing-complete they can also be used to let the compiler resolve recursive conditionals and generate substantial programs through template metaprogramming.

Dynamic polymorphism

Inheritance
Variable pointers (and references) to a base class type in C++ can refer to objects of any derived classes of that type in addition to objects exactly matching the variable type. This allows arrays and other kinds of containers to hold pointers to objects of differing types. Because assignment of values to variables usually occurs at run-time, this is necessarily a run-time phenomenon.

C++ also provides a dynamic_cast operator, which allows the program to safely attempt conversion of an object into an object of a more specific object type (as opposed to conversion to a more general type, which is always allowed). This feature relies on run-time type information (RTTI). Objects known to be of a certain specific type can also be cast to that type with static_cast, a purely compile-time construct which is faster and does not require RTTI.

Virtual member functions
Ordinarily when a function in a derived class overrides a function in a base class, the function to call is determined by the type of the object. A given function is overridden when there exists no difference, in the number or type of parameters, between two or more definitions of that function. Hence, at compile time it may not be possible to determine the type of the object and therefore the correct function to call, given only a base class pointer; the decision is therefore put off until runtime. This is called dynamic dispatch. Virtual member functions or methods allow the most specific implementation of the function to be called, according to the actual run-time type of the object. In C++, this is commonly done using virtual function tables. If the object type is known, this may be bypassed by prepending a fully qualified class name before the function call, but in general calls to virtual functions are resolved at run time.

In addition to standard member functions, operator overloads and destructors can be virtual. A general rule of thumb is that if any functions in the class are virtual, the destructor should be as well. As the type of an object at its creation is known at compile time, constructors, and by extension copy constructors, cannot be virtual. Nonetheless a situation may arise where a copy of an object needs to be created when a pointer to a derived object is passed as a pointer to a base object. In such a case a common solution is to create a clone() (or similar) function and declare that as virtual. The clone() method creates and returns a copy of the derived class when called.

A member function can also be made "pure virtual" by appending it with = 0 after the closing parenthesis and before the semicolon. Objects cannot be created of a class with a pure virtual function and are called abstract data types. Such abstract data types can only be derived from. Any derived class inherits the virtual function as pure and must provide a non-pure definition of it (and all other pure virtual functions) before objects of the derived class can be created. An attempt to create an object from a class with a pure virtual function or inherited pure virtual function will be flagged as a compile-time error.

Parsing and processing C++ source code
It is relatively difficult to write a good C++ parser with classic parsing algorithms such as LALR. This is partly because the C++ grammar is not LALR. Because of this, there are very few tools for analyzing or performing non-trivial transformations (e.g., refactoring) of existing code. One way to handle this difficulty is to choose a different syntax, such as Significantly Prettier and Easier C++ Syntax, which is LALR parsable. More powerful parsers, such as GLR parsers, can be substantially simpler (though slower).

Parsing (in the literal sense of producing a syntax tree) is not the most difficult problem in building a C++ processing tool. Such tools must also have the same understanding of the meaning of the identifiers in the program as a compiler might have. Practical systems for processing C++ must then not only parse the source text, but be able to resolve for each identifier precisely which definition applies (e.g. they must correctly handle C++'s complex scoping rules) and what its type is, as well as the types of larger expressions.

Finally, a practical C++ processing tool must be able to handle the variety of C++ dialects used in practice (such as that supported by the GNU Compiler Collection and that of Microsoft's Visual C++) and implement appropriate analyzers, source code transformers, and regenerate source text. Combining advanced parsing algorithms such as GLR with symbol table construction and program transformation machinery can enable the construction of arbitrary C++ tools.

Compatibility
Producing a reasonably standards-compliant C++ compiler has proven to be a difficult task for compiler vendors in general. For many years, different C++ compilers implemented the C++ language to different levels of compliance to the standard, and their implementations varied widely in some areas such as partial template specialization. Recent releases of most popular C++ compilers support almost all of the C++ 1998 standard.

One particular point of contention is the export keyword, intended to allow template definitions to be separated from their declarations. The first compiler to implement export was Comeau C/C++, in early 2003 (5 years after the release of the standard); in 2004, the beta compiler of Borland C++ Builder X was also released with export. Both of these compilers are based on the EDG C++ front end. It should also be noted that many C++ books provide example code using the keyword export (for example, Beginning ANSI C++ by Ivor Horton) which will not compile in most compilers, but there is no reference to the problem with the keyword export mentioned. Other compilers such as GCC do not support it at all. Herb Sutter, former convener of the C++ standards committee, recommended that export be removed from future versions of the C++ standard, but finally the decision was made to retain it.

In order to give compiler vendors greater freedom, the C++ standards committee decided not to dictate the implementation of name mangling, exception handling, and other implementation-specific features. The downside of this decision is that object code produced by different compilers is expected to be incompatible. There are, however, third party standards for particular machines or operating systems which attempt to standardize compilers on those platforms (for example C++ ABI); some compilers adopt a secondary standard for these items.

19) HISTORY OF COMPUTER 'S PERIPHERAL DEVICES

2009-06-19T15:50:00.000-07:00

This category focuses on the history and timeline of various items used in computers, Each item is explained in general, providing information suitable for everyone from beginners to advanced users.
Take a cruise through history to discover some of the key developments that have brought us to our present state of computing, including the development of numbers, the introduction of mechanical aids to calculation, the evolution of electronics, and the impact of electronics on computing.
No one person may be credited with the invention of computers, but several names stand proud in the crowd. The following offers some of the more notable developments and individuals, with great regret for any omissions.

1- CR- ROMS

CD-R is an abbreviation of compact disc recordable. Operating on the same premise as a CD, a CD-R is thin disc made of polycarbonate with 120mm diameter used to store music or data. However, unlike conventional CD media, a CD-R has dye core instead of a metal core. A laser is used to etch "pits" into the dye so that the disc can later be read by the laser in a CD-ROM drive or CD player. Once used, a CD-R cannot be erased and reused, but it can be recorded in multiple sessions by using UDF format. A cdrw, though, can be reused.
There was some incompatability with CD-R and older CD-ROM drives. This was primarily due to the lower reflectivity of the CD-R disc. In general, CD drives marked as 8x or greater will usually read CD-R discs.

2- DVD ROMS

DVD started as the Digital Video Disc but now means Digital Versatile Disc or just DVD. It is a multi-application family of optical disc formats for read-only, recordable and re-writable applications. The main features of the DVD formats are:
Backwards compatibility with current CD media. All DVD hardware will play audio CDs and CD-ROMs (although not all hardware will play CD-Rs or CD-RWs).
Physical dimensions identical to compact disc but using two 0.6 mm thick substrates, bonded together.
Single-layer/dual-layer and single/double sided options.
Up to 4.7 GB read-only capacity per layer, 8.5 GB per side maximum.
Designed from the outset for video, audio and multimedia, not just audio.
All formats use a common file system (UDF).
Digital and analogue copy protection for DVD-Video and DVD-Audio built into standard.
Recordable and re-writable versions are part of the family.
DVD started in 1994 as two competing formats, Super Disc (SD) and Multimedia CD (MMCD). DVD now is the result of an agreement by both camps on a single standard to meet the requirements of all the various industries involved.

3- FLOPPY DISKETTES

In 1971, an IBM team led by Alan Shugart invented the 8-inch floppy diskette. This floppy was an 8" plastic disk coated with magnetic iron oxide; data was written to and read from the disk's surface. The nickname "floppy" came from it's flexibility. The floppies were considered revolutionary devices at the time for its portability which provided a new and easy physical means of transporting data from one computer to another.
A floppy disk is a circle of magnetic material similar to any kind of recording tape; one or two sides of the disk are used for recording. The disk drive grabs the floppy by its center and spins it like a record inside its housing. The read/write head, much like the head on a tape deck, contacts the surface through an opening in the plastic shell, or envelope.

4- HARD DISK DRIVES

The hard disk drive has short and fascinating history. In 24 years it evolved from a monstrosity with fifty, two foot diameter disks holding five MBytes (5,000 bytes) of data to today's drives measuring 3 /12 inches wide and an inch high (and smaller) holding more than 70 GBytes (70,000,000,000 bytes/characters). Here, then, is the short history of this marvelous device.
Before the disk drive there were drums... In 1950 Engineering Research Associates of Minneapolis built the first commercial magnetic drum storage unit for the U.S. Navy, the ERA 110. It could store one million bits of data and retrieve a word in 5 thousandths of a second.
In 1956 IBM invented the first computer disk storage system, the 305 RAMAC (Random Access Method of Accounting and Control). This system could store five MBytes. It had fifty, 24-inch diameter disks!
By 1961 IBM had invented the first disk drive with air bearing heads and in 1963 they introduced the removable disk pack drive. In 1970 the eight inch floppy disk drive was introduced by IBM. My first floppy drives were made by Shugart who was one of the "dirty dozen" who left IBM to start their own companies. In 1981 two Shugart 8 inch floppy drives with enclosure and power supply cost me about $350.00. They were for my second computer. My first computer had no drives at all.
In 1973 IBM shipped the model 3340 Winchester sealed hard disk drive, the predecessor of all current hard disk drives. The 3340 had two spindles each with a capacity of 30 MBytes, and the term "30/30 Winchester" was thus coined.
Seagate ST4053 40 MByte 5 1/4 inch, full-height "clunker" with ST506 interface and voice coil circa 1987. My cost was $435.00. In 1980, Seagate Technology introduced the first hard disk drive for microcomputers, the ST506. It was a full height (twice as high as most current 5 1/4" drives) 5 1/4" drive, with a stepper motor, and held 5 Mbytes. My first hard disk drive was an ST506. I cannot remember exactly how much it cost, but it plus its enclosure, etc. was well over a thousand dollars. It took me three years to fill the drive. Also, in 1980 Phillips introduced the first optical laser drive. In the early 80's, the first 5 1/4" hard disks with voice coil actuators (more on this later) started shipping in volume, but stepper motor drives continued in production into the early 1990's. In 1981, Sony shipped the first 3 1/2" floppy drives.
In 1983 Rodime made the first 3.5 inch rigid disk drive. The first CD-ROM drives were shipped in 1984, and "Grolier's Electronic Encyclopedia," followed in 1985. The 3 1/2" IDE drive started it's existence as a drive on a plug-in expansion board, or "hard card." The hard card included the drive on the controller which, in turn, evolved into Integrated Device Electronics (IDE) hard disk drive, where the controller became incorporated into the printed circuit on the bottom of the hard disk drive. Quantum made the first hard card in 1985.
In 1986 the first 3 /12" hard disks with voice coil actuators were introduced by Conner in volume, but half (1.6") and full height 5 1/4" drives persisted for several years. In 1988 Conner introduced the first one inch high 3 1/2" hard disk drives. In the same year PrairieTek shipped the first 2 1/2" hard disks.
In 1997 Seagate introduced the first 7,200 RPM, Ultra ATA hard disk drive for desktop computers and in February of this year they introduced the first 15,000 RPM hard disk drive, the Cheetah X15. Milestones for IDE DMA, ATA/33, and ATA/66 drives follow: 1994 DMA, Mode 2 at 16.6 MB/s -- 1997 Ultra ATA/33 at 33.3 MB/s -- 1999 Ultra ATA/66 at 66.6 MB/s

5- IDE ( INTELLIGENT DRIVER ELECTRONICS)

Compaq started the development of the IDE interface. This standard was designed specially for the IBM PC and can achieve high data transfer rates through a 1:1 interleave factor and caching by the actual disk controller - the bottleneck is often the old AT bus and the drive may read data far quicker than the bus can accept it, so the cache is used as a buffer. Theoretically 1MBps is possible but 700KBps is perhaps more typical of such drives. This standard has been adopted by many other models of computer, such the Acorn Archimedes A4000 and above. A later improvement was EIDE, laid down in 1989, which also removed the maximum drive size of 528MB and increased data transfer rates.

6- MODEMs

Modem, device that converts between analog and digital signals. Digital signals, which are used by computers, are made up of separate units, usually represented by a series of 1's and 0's. Analog signals vary continuously; an example of an analog signal is a sound wave. Modems are often used to enable computers to communicate with each other across telephone lines. A modem converts the digital signals of the sending computer to analog signals that can be transmitted through telephone lines. When the signal reaches its destination, another modem reconstructs the original digital signal, which is processed by the receiving computer. If both modems can transmit data to each other simultaneously, the modems are operating in full duplex mode; if only one modem can transmit at a time, the modems are operating in half duplex mode.
To convert a digital signal to an analog one, the modem generates a carrier wave and modulates it according to the digital signal. The kind of modulation used depends on the application and the speed of operation for which the modem is designed. For example, many high-speed modems use a combination of amplitude modulation, where the amplitude of the carrier wave is changed to encode the digital information, and phase modulation, where the phase of the carrier wave is changed to encode the digital information. The process of receiving the analog signal and converting it back to a digital signal is called demodulation. The word "modem" is a contraction of its two basic functions: modulation and demodulation.
Dennis C. Hayes invented the PC modem in 1977, establishing the critical technology that allowed today's online and Internet industries to emerge and grow. He sold the first Hayes modem products to computer hobbyists in April of 1977 and founded D.C. Hayes Associates, Inc., the company known today as Hayes Corp., in January of 1978. Hayes quality and innovation resulted in performance enhancements and cost reductions that led the industry in the conversion from leased line modems to intelligent dial modems - the PC Modem.
Hayes-Compatible, in computer science, an adjective used to describe a modem that responds to the same set of commands as a modem manufactured by Hayes Microcomputer Products, originators of the de facto standard for microcomputer modems.

7- MONITORS

Often referred to as a monitor when packaged in a separate case, the display is the most-used output device on a computer. The display provides instant feedback by showing your text and graphic images as you work or play. Most desktop displays use a cathode ray tube (CRT), while portable computing devices such as laptops incorporate liquid crystal display (LCD), light-emitting diode (LED), gas plasma or other image projection technology. Because of their slimmer design and smaller energy consumption, monitors using LCD technologies are beginning to replace the venerable CRT on many desktops.
Displays have come a long way since the blinking green monitors in text-based computer systems of the 1970s. Just look at the advances made by IBM over the course of a decade: In 1981, IBM introduced the Color Graphics Adapter (CGA), which was capable of rendering four colors, and had a maximum resolution of 320 pixels horizontally by 200 pixels vertically. IBM introduced the Enhanced Graphics Adapter (EGA) display in 1984. EGA allowed up to 16 different colors and increased the resolution to 640x350 pixels, improving the appearance of the display and making it easier to read text. In 1987, IBM introduced the Video Graphics Array (VGA) display system. Most computers today support the VGA standard and many VGA monitors are still in use. IBM introduced the Extended Graphics Array (XGA) display in 1990, offering 800x600 pixel resolution in true color(16.8 million colors) and 1,024x768 resolution in 65,536 colors. Most displays sold today support the Ultra Extended Graphics Array (UXGA) standard. UXGA can support palette of up to 16.8 million colors and resolutions of up to 1600x1200 pixels, depending on the video memory of the graphics card in your computer. The maximum resolution normally depends on the number of colors displayed. For example, your card might require that you choose between 16.8 million colors at 800x600, or 65,536 colors at 1600x1200.
The combination of the display modes supported by your graphics adapter and the color capability of your monitor determine how many colors can be displayed. For example, a display that can operate in SuperVGA (SVGA) mode can display up to 16,777,216 (usually rounded to 16.8 million) colors because it can process a 24-bit-long description of a pixel. The number of bits used to describe a pixel is known as its bit depth. With a 24-bit bit depth, 8 bits are dedicated to each of the three additive primary colors -- red, green and blue. This bit depth is also called true color because it can produce the 10,000,000 colors discernible to the human eye, while a 16-bit display is only capable of produ cing 65,536 colors. Displays jumped from 16-bit color to 24-bit color because working in 8-bit increments makes things a whole lot easier for developers and programmers.
Briefly, the measure of how much space there is between a display's pixels. When considering dot pitch, remember that smaller is better. Packing the pixels closer together is fundamental to achieving higher resolutions. A display normally can support resolutions that match the physical dot (pixel) size as well as several lesser resolutions. For example, a display with a physical grid of 1280 rows by 1024 columns can obviously support a maximum resolution of 1280x1024 pixels. It usually also supports lower resolutions such as 1024x768, 800x600, and 640x480.
In monitors based on CRT technology, the refresh rate is the number of times that the image on the display is drawn each second. If your CRT monitor has a refresh rate of 72 Hertz (Hz), then it cycles through all the pixels from top to bottom 72 times a second. Refresh rates are very important because they control flicker, and you want the refresh rate as high as possible. Too few cycles per second and you will notice a flickering, which can lead to headaches and eye strain.

8- MOUSE POINTERS

Years before personal computers and desktop information processing became commonplace or even practicable, Douglas Engelbart had invented a number of interactive, user-friendly information access systems that we take for granted today: the computer mouse was one of his inventions. At the Fall Joint Computer Conference in San Francisco in 1968, Engelbart astonished his colleagues by demonstrating the aforementioned systems---using an utterly primitive 192 kilobyte mainframe computer located 25 miles away! Engelbart has earned nearly two dozen patents, the most memorable being perhaps for his "X-Y Position Indicator for a Display System": the prototype of the computer "mouse" whose convenience has revolutionized personal computing.
Mouse (computer), a common pointing device, popularized by its inclusion as standard equipment with the Apple Macintosh. With the rise in popularity of graphical user interfaces in MS-DOS; UNIX, and OS/2, use of mice is growing throughout the personal computer and workstation worlds. The basic features of a mouse are a casing with a flat bottom, designed to be gripped by one hand; one or more buttons on the top; a multidirectional detection device (usually a ball) on the bottom; and a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk), the user typically controls an on-screen cursor. A mouse is a relative pointing device because there are no defined limits to the mouse's movement and because its placement on a surface does not map directly to a specific screen location. To select items or choose commands on the screen, the user presses one of the mouse's buttons, producing a "mouse click."
Mouse Patent # 3,541,541 issued 11/17/70 for X-Y Position Indicator For A Display System Douglas Engelbart's patent for the mouse is only a representation of his pioneering work in the design of modern interactive computer environments.

9- PLOTTERS

A plotter is a vector graphics printing device that connects to a computer.
Plotters print their output by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art, rather than raster graphics as with other printers. They can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pens.
Another difference between plotters and printers is that a printer is aimed primarily at printing text. This makes it fairly easy to control, simply sending the text to the printer is usually enough to generate a page of output. This is not the case of the line art on a plotter, where a number of printer control languages were created to send the more detailed information like "draw a line from here to here". The most popular of these is likely HPGL.
Early plotters were created by attaching ball-point pens to drafting pantographs and driving the machines with motors controlled by the computer. This had the disadvantage of being somewhat slow to move, as well as requiring floor space equal to the size of the paper. Later versions worked by placing the paper over a roller which moved the paper back and forth for X motion, while the pen moved back and forth on a single arm for Y motion. Another change was the addition of an elecrtically controlled clamp to hold the pens, which allowed them to be changed and thus create multi-colored output.
For a time in the 1980's smaller "home-use" plotters became popular for experimentation in computer graphics. But their low speed meant they were not useful for general printing purposes, and you would need another conventional printer for those jobs. With the widespread availability of high-resolution inkjets and laser printers, plotters have all but disappeared.
Plotters are used primarily in drafting and CAD applications, where they have the advantage of working on very large paper sizes while maintaining high resolution. Another use has been found by replacing the pen with a cutter, and in this form plotters can be found in many garment and sign shops.

10- SOUND CARDS

Computers were never designed to handle sound. About the only audio you'd hear from an early computer were beeps, designed to tell you if there was a problem. Computer games manipulated these beeps, to produce truly awful music as an accompaniment to games like Space Invaders. However, surely there was more to sounds than beeps? Thankfully a company from the Far East recognised this, and made the original Sound Blaster sound card for the now ancient ISA bus. It could record real audio and play it back, something of a quantum leap. It also had a MIDI interface, still common on sound cards today, which could control synthesisers, samplers and other electronic music equipment. It could "create" sounds by using FM synthesis, which were not that realistic but were nevertheless better than simple beeps. The quality of the audio was 8 bit 11 kHz, so sounded roughly like an AM radio.
The sound card is quite a complicated piece of electronics. The most important parts are the ADC and DAC. The ADC (Analogue-to-Digital convertor) takes in analogue signals, for example from a microphone and converts them to digital signals for the computer to store. The DAC (Digital-to-Analogue convertor) does the opposite. However, in the future there will be no need for either, since both speakers and microphones will be able to directly record and playback digital signals directly. The heart of a CD player is also the DAC. CD players tend to sound better than the average, because they generally cost more and are simpler devices. Hence the DAC component of a CD player tends to be more expensive (and thus better quality). Having said that, the quality of DACs on sound cards is improving all the time.
The advantage of digital audio (ie. storing audio as 1s and 0s) is that no matter how many times it is copied it remains identical, and does not degrade like analogue sources, such as vinyl. The next major development for sound cards was the leap up to 16 bit 44.1 kHz stereo audio, ie. CD quality. However, this posed problems for the archaeic ISA bus, which had problems playing back and recording more than one track at the same time. This effectively meant it was difficult to use your computer to make phone calls on the internet (since you couldn't talk and hear at the same time!) or use it as a multitrack audio editor (for musicians). The PCI bus solved this problem. Nowadays virtually all soundcards are PCI. Currently we are seeing 24 bit 96 kHz sound cards emerging, which promise even better sound quality than CDs! Some sound cards also decode Dolby Digital sound, so you can connect computer speakers to them for surround sound, when playing back DVDs. High-end sound cards also come with digital inputs and outputs, letting you bypass the sound cards convertors and use external ones.
Recently there has been the advent of the USB and Firewire buses. These enable you to connect fast external devices to your computer. Sound cards attached to the USB bus cannot playback as many tracks simultaneously as a PCI sound card. However, for people other than musicans this is hardly relevant. Also being external they can be used on more than one machine and on laptops, which notoriously have poor sound cards. There are also several external Firewire sound cards. These are quite expensive and designed to playback and record many tracks. Consequently they are a waste of money if all you do is watch DVDs or play MP3s on your computer.
Sound on the PC has come a long way since all those beeps twenty years ago!

11- TOUCH SCREENS

A touch screen is a special type of visual display unit with a screen which is sensitive to pressure or touching. The screen can detect the position of the point of touch. The design of touch screens is best for inputting simple choices and the choices are programmable. The device is very user-friendly since it 'talks' with the user when the user is picking up choices on the screen.
Touch technology turns a CRT, flat panel display or flat surface into a dynamic data entry device that replaces both the keyboard and mouse. In addition to eliminating these separate data entry devices, touch offers an "intuitive" interface. In public kiosks, for example, users receive no more instruction than 'touch your selection.'
Specific areas of the screen are defined as "buttons" that the operator selects simply by touching them. One significant advantage to touch screen applications is that each screen can be customized to reflect only the valid options for each phase of an operation, greatly reducing the frustration of hunting for the right key or function.
Pen-based systems, such as the Palm Pilot® and signature capture systems, also use touch technology but are not included in this article. The essential difference is that the pressure levels are set higher for pen-based systems than for touch.
Touch screens come in a wide range of options, from full color VGA and SVGA monitors designed for highly graphic Windows® or Macintosh® applications to small monochrome displays designed for keypad replacement and enhancement.
Specific figures on the growth of touch screen technology are hard to come by, but a 1995 study last year by Venture Development Corporation predicted overall growth of 17%, with at least 10% in the industrial sector.
According to Jim Sido, IBM's National Marketing Manager for Food Service Products, this year should see even greater growth than last year.
John Muhlberger, Director of Product Management at PAR Microsystems estimated that, for POS applications, touch screen terminals outsell keyboard terminals about 4:1, even though the touch terminals cost somewhat more.
Other vendors agree that touch screen technology is becoming more popular because of its ease-of-use, proven reliability, expanded functionality, and decreasing cost.

18) HISTORY OF PRINTING

2009-06-19T15:36:00.000-07:00

The history of printing began as an attempt to make easier and reduce the cost of reproducing multiple copies of documents, fabrics, wall papers and so on. Printing streamlined the process of communication, and contributed to the development of commerce, law, religion and culture.

1- WOODBLOCK PRINTING
Woodblock printing is a technique for printing text, images or patterns used widely throughout East Asia and originating in China in antiquity as a method of printing on textiles and later paper. As a method of printing on cloth, the earliest surviving examples from China date to before 220, and from Egypt to the 4th century. Ukiyo-e is the best known type of Japanese woodblock art print. Most European uses of the technique on paper are covered by the art term woodcut, except for the block-books produced mainly in the fifteenth century.

Yuan Dynasty woodblock edition of a Chinese play

The use of round "cylinder seals" for rolling an impress onto clay tablets goes back to early Mesopotamian civilization before 3,000 BCE, where they are the most common works of art to survive, and feature complex and beautiful images. In both China and Egypt, the use of small stamps for seals preceded the use of larger blocks. In Egypt, Europe and India, the printing of cloth certainly preceded the printing of paper or papyrus; this was probably also the case in China. The process is essentially the same - in Europe special presentation impressions of prints were often printed on silk until at least the seventeenth century.

1.1- In China
The earliest woodblock printed fragments to survive are from China and are of silk printed with flowers in three colours from the Han dynasty (before 220 CE). The earliest Egyptian printed cloth dates from the 4th century.

It is clear that the Chinese were the first by several centuries to use the process to print solid text, and equally that, much later, in Europe the printing of images on cloth developed into the printing of images on paper (woodcuts). It is also now established that the use in Europe of the same process to print substantial amounts of text together with images in block-books only came after the development of movable type in the 1450s.

1.2- In the Islamic world
Block printing, called tarsh in Arabic was developed in Arabic Egypt during the 9th-10th centuries, mostly for prayers and amulets. It is unclear whether the print blocks were made from metal or wood or other materials. This technique, however, appears to have had very little influence outside of the Muslim world. Though Europe adopted woodblock printing from the Muslim world, initially for fabric, the technique of metal block printing was also unknown in Europe. Block printing later went out of use in Islamic Central Asia after movable type printing was introduced from China.

1.3- In Europe
Block printing first came to Christian Europe as a method for printing on cloth, where it was common by 1300. Images printed on cloth for religious purposes could be quite large and elaborate, and when paper became relatively easily available, around 1400, the medium transferred very quickly to small woodcut religious images and playing cards printed on paper. These prints were produced in very large numbers from about 1425 onwards.

Around the mid-century, block-books, woodcut books with both text and images, usually carved in the same block, emerged as a cheaper alternative to manuscripts and books printed with movable type. These were all short heavily illustrated works, the bestsellers of the day, repeated in many different block-book versions: the Ars moriendi and the Biblia pauperum were the most common. There is still some controversy among scholars as to whether their introduction preceded or, the majority view, followed the introduction of movable type, with the range of estimated dates being between about 1440–1460.

The volume of Joseph Needham's Science and Civilization in China dealing with Paper and printing has a chapter that suggests that "European block printers must not only have seen Chinese samples, but perhaps had been taught by missionaries or others who had learned these un-European methods from Chinese printers during their residence in China.", but he also admitted that the "only evidence of European printing transmitted from China is a lack of counterevidence". However, paper itself was needed for the printing process and this came to Europe via trade with the Arabs from China. Historians acknowledge that paper indeed came from China without which printing would have been impossible, however, there is less direct evidence of the influence of printing technology from Asia and its influence on European printing technology.

2- STENCIL
Stencils may have been used to color cloth for a very long time; the technique probably reached its peak of sophistication in Katazome and other techniques used on silks for clothes during the Edo period in Japan. In Europe, from about 1450 they were very commonly used to colour old master prints printed in black and white, usually woodcuts. This was especially the case with playing-cards, which continued to be coloured by stencil long after most other subjects for prints were left in black and white. Stenciling back in the 2600 BC's was different. They used color from plants and flowers such as indigo (which extracts blue). Stencils were used for mass publications, as the type didn't have to be hand-written.

3- MOVABLE TYPE
Movable type is the system of printing and typography using movable pieces of metal type, made by casting from matrices struck by letterpunches.

Around 1040, the first known movable type system was created in China by Bi Sheng out of porcelain. Metal movable type was first invented in Korea during the Goryeo Dynasty (around 1230). Neither movable type system was widely used, one reason being the enormous Chinese character set.

A case of cast metal type pieces and typeset matter in a composing stick

It is traditionally summarized that Johannes Gutenberg, of the German city of Mainz, developed European movable type printing technology around 1439 and in just over a decade, the European age of printing began. However, the details show a more complex evolutionary process spread over multiple locations. Also, Johann Fust and Peter Schöffer experimented with Gutenberg in Mainz.

Compared to woodblock printing, movable type page-setting was quicker and more durable. The metal type pieces were more durable and the lettering was more uniform, leading to typography and fonts. The high quality and relatively low price of the Gutenberg Bible (1455) established the superiority of movable type, and printing presses rapidly spread across Europe, leading up to the Renaissance, and later all around the world. Today, practically all movable type printing ultimately derives from Gutenberg's movable type printing, which is often regarded as the most important invention of the second millennium.

Gutenberg is also credited with the introduction of an oil-based ink which was more durable than previously used water-based inks. Having worked as a professional goldsmith, Gutenberg made skillful use of the knowledge of metals he had learned as a craftsman. Gutenberg was also the first to make his type from an alloy of lead, tin, and antimony, known as type metal, printer's lead, or printer's metal, which was critical for producing durable type that produced high-quality printed books, and proved to be more suitable for printing than the clay, wooden or bronze types used in East Asia. To create these lead types, Gutenberg used what some considered his most ingenious invention, a special matrix wherewith the moulding of new movable types with an unprecedented precision at short notice became feasible. Within a year of printing the Gutenberg Bible, Gutenberg also published the first coloured prints.

The invention of the printing press revolutionized communication and book production leading to the spread of knowledge. Rapidly, printing spread from Germany by emigrating German printers, but also by foreign apprentices returning home. A printing press was built in Venice in 1469, and by 1500 the city had 417 printers. In 1470 Johann Heynlin set up a printing press in Paris. In 1473 Kasper Straube published the Almanach cracoviense ad annum 1474 in Kraków. Dirk Martens set up a printing press in Aalst (Flanders) in 1473. He printed a book about the two lovers of Enea Piccolomini who became pope Pius II.In 1476 a printing press was set up in England by William Caxton. Belarusian Francysk Skaryna printed the first book in Slavic language on August 6, 1517. The Italian Juan Pablos set up an imported press in Mexico City in 1539. The first printing press in Southeast Asia was set up in the Philippines by the Spanish in 1593. Stephen Day was the first to build a printing press in North America at Massachusetts Bay in 1638, and helped establish the Cambridge Press.

The Gutenberg press was much more efficient than manual copying and still was largely unchanged in the eras of John Baskerville and Giambattista Bodoni, over 300 years later. By 1800, Lord Stanhope had constructed a press completely from cast iron, reducing the force required by 90% while doubling the size of the printed area. While Stanhope's "mechanical theory" had improved the efficiency of the press, it still was only capable of 250 sheets per hour. German printer Friedrich Koenig would be the first to design a non-manpowered machine—using steam. Having moved to London in 1804, Koenig soon met Thomas Bensley and secured financial support for his project in 1807. Patented in 1810, Koenig had designed a steam press "much like a hand press connected to a steam engine." The first production trial of this model occurred in April 1811.

3.1- Flat-bed printing press
A printing press is a mechanical device for applying pressure to an inked surface resting upon a medium (such as paper or cloth), thereby transferring an image. The systems involved were first assembled in Germany by the goldsmith Johann Gutenberg in the mid-15th century. Printing methods based on Gutenberg's printing press spread rapidly throughout first Europe and then the rest of the world, replacing most block printing and making it the sole progenitor of modern movable type printing. As a method of creating reproductions for mass consumption, The printing press has been superseded by the advent of offset printing.

Printing press from 1811, photographed in Munich, Germany

Johannes Gutenberg's work in the printing press began in approximately 1436 when he partnered with Andreas Dritzehen—a man he had previously instructed in gem-cutting—and Andreas Heilmann, owner of a paper mill. It was not until a 1439 lawsuit against Gutenberg that official record exists; witnesses testimony discussed type, an inventory of metals (including lead) and his type mold.

Others in Europe were developing movable type at this time, including goldsmith Procopius Waldfoghel of France and Laurens Janszoon Coster of the Netherlands. They are not known to have contributed specific advances to the printing press. While the Encyclopædia Britannica Eleventh Edition had attributed the invention of the printing press to Coster, the company now states that is incorrect.

4- PRINTING HOUSES
Early printing houses (near the time of Gutenberg) were run by "master printers." These printers owned shops, selected and edited manuscripts, determined the sizes of print runs, sold the works they produced, raised capital and organized distribution. Some master printing houses, like that of Aldus Manutius, became the cultural centre for literati such as Erasmus.

Print shop apprentices: Apprentices, usually between the ages of 15 and 20, worked for master printers. Apprentices were not required to be literate, and literacy rates at the time were very low, in comparison to today. Apprentices prepared ink, dampened sheets of paper, and assisted at the press. An apprentice who wished to learn to become a compositor had to learn Latin and spend time under the supervision of a journeyman.
Journeyman printers: After completing their apprenticeships, journeyman (so called from the French "journée" for day) printers were free to move employers. This facilitated the spread of printing to areas that were less print-centred.

Compositors: Those who set the type for printing.

Pressmen: the person who worked the press. This was physically labour intensive.

The earliest-known image of a European, Gutenberg-style print shop is the Dance of Death by Matthias Huss, at Lyon, 1499. This image depicts a compositor standing at a compositor's case being grabbed by a skeleton. The case is raised to facilitate his work. The image also shows a pressman being grabbed by a skeleton. At the right of the printing house a bookshop is shown.

4.1- Financial aspects
Court records from the city of Mainz document that Johannes Fust was, for some time, Gutenberg's financial backer.

By the sixteenth century jobs associated with printing were becoming increasingly specialized. Structures supporting publishers were more and more complex, leading to this division of labour. In Europe between 1500 and 1700 the role of the Master Printer was dying out and giving way to the bookseller—publisher. Printing during this period had a stronger commercial imperative than previously. Risks associated with the industry however were substantial, although dependent on the nature of the publication.

Bookseller publishers negotiated at trade fairs and at print shops. Jobbing work appeared in which printers did menial tasks in the beginning of their careers to support themselves.

1500–1700: Publishers developed several new methods of funding projects.

1.Cooperative associations/publication syndicates—a number of individuals shared the risks associated with printing and shared in the profit. This was pioneered by the French.

2.Subscription publishing—pioneered by the English in the early 17th century. A prospectus for a publication was drawn up by a publisher to raise funding. The prospectus was given to potential buyers who signed up for a copy. If there were not enough subscriptions the publication did not go ahead. Lists of subscribers were included in the books as endorsements. If enough people subscribed a reprint might occur. Some authors used subscription publication to bypass the publisher entirely.

3.Installment publishing—books were issued in parts until a complete book had been issued. This was not necessarily done with a fixed time period. It was an effective method of spreading cost over a period of time. It also allowed earlier returns on investment to help cover production costs of subsequent installments.
The Mechanick Exercises, by Joseph Moxon, in London, 1683, was said to be the first publication done in installments.

Publishing trade organizations allowed publishers to organize business concerns collectively. Systems of self-regulation occurred in these arrangements. For example, if one publisher did something to irritate other publishers he would be controlled by peer pressure. Such systems are known as cartels, and are in most countries now considered to be in restraint of trade. These arrangements helped deal with labour unrest among journeymen, who faced difficult working conditions. Brotherhoods predated unions, without the formal regulations now associated with unions.

5- ROTARY PRINTING PRESS
A rotary printing press is a printing press in which the impressions are curved around a cylinder so that the printing can be done on long continuous rolls of paper, cardboard, plastic, or a large number of other substrates. Rotary drum printing was invented by Richard March Hoe in 1847, and then significantly improved by William Bullock in 1863.

6- INTAGLIO

Intaglio (pronounced in-TAL-yo) is a family of printmaking techniques in which the image is incised into a surface, known as the matrix or plate. Normally, copper or zinc plates are used as a surface, and the incisions are created by etching, engraving, drypoint, aquatint or mezzotint. Collographs may also be printed as intaglio plates. To print an intaglio plate the surface is covered in thick ink and then rubbed with tarlatan cloth to remove most of the excess. The final smooth wipe is usually done by hand, sometimes with the aid of newspaper or old public phone book pages, leaving ink only in the incisions. A damp piece of paper is placed on top and the plate and paper are run through a printing press that, through pressure, transfers the ink from the recesses of the plate to the paper.

7- LITHOGRAPHY ( 1796)

Invented by Bavarian author Aloys Senefelder in 1796, lithography is a method for printing on a smooth surface. Lithography is a printing process that uses chemical processes to create an image. For instance, the positive part of an image would be a hydrophobic chemical, while the negative image would be water. Thus, when the plate is introduced to a compatible ink and water mixture, the ink will adhere to the positive image and the water will clean the negative image. This allows for a relatively flat print plate which allows for much longer runs than the older physical methods of imaging (e.g., embossing or engraving).

An example of a 19th century lithograph depicting royal Afghan soldiers of the Durrani Empire in Afghanistan

8- CHROMOLITHOGRAPHY

Chromolithography was the first method for making true multi-color prints. Earlier attempts at polychromed printing relied on hand-coloring. The type of color printing stemmed from the process of lithography, and it includes all types of lithography that are printed in color. It replaced coloring prints by hand, and eventually served as a replica of a real painting. Lithographers sought to find a way to print on flat surfaces with the use of chemicals instead of relief or intaglio printing. Depending on the amount of colors present, a chromolithograph could take months to produce. To make what was once referred to as a “’chromo’”, a lithographer, with a finished painting in front of him, gradually built and corrected the print to look as much as possible like the painting in front of him, sometimes using dozens of layers. The process can be very time consuming and cumbersome contingent upon the skill of the lithographer.

1872 chromolithograph of roadside inn, published in Maryland

The technique for using color in printing was invented in 1796 in Germany. Considering the fact that it stemmed from lithography, there have been debates over whether chromolithography was created by Alois Senefelder, the same person who came up with printing by way of lithography. Senefelder introduced colored lithography in his 1818 Vollstaendiges Lehrbuch der Steindruckerey (A Complete Course of Lithography), and in the work, Senefelder told of his plans to print using color and he also explained the colors he wished to be able to print someday. Although Senefelder recorded ideas on chromolithography, it turns out that other countries besides Germany, such as France and England, were also heavily involved in trying to find a new way to print in color. Godefroy Engelmann of Mulhouse proved to be one of the few searching for ways to produce colored printed images when he was awarded his patent on chromolithography in July 1837. Even after Engelmann received his award, disputes over whether chromolithography was already being used continued to rise. Some sources point to the idea that chromolithography was already being used in areas of printing such as the production of playing cards.

9- OFFSET PRESS ( 1870s)

Offset printing is a widely used printing technique where the inked image is transferred (or "offset") from a plate to a rubber blanket, then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a film of water, keeping the non-printing areas ink-free.

10- SCREEN PRINTING (1907)

Screenprinting has its origins in simple stencilling, most notably of the Japanese form (katazome), used who cut banana leaves and inserted ink through the design holes on textiles, mostly for clothing. This was taken up in France. The modern screenprinting process originated from patents taken out by Samuel Simon in 1907 in England. This idea was then adopted in San Francisco, California, by John Pilsworth in 1914 who used screenprinting to form multicolor prints in a subtractive mode, differing from screenprinting as it is done today.

11- FLEXOGRAPHY

Flexography (also called surface printing), often abbreviated to flexo, is a method of printing most commonly used for packaging (Labels, Tape, Bags, Boxes, Banners, Etc).

A flexo print is achieved by creating a mirrored master of the required image as a 3D relief in a rubber or polymer material. A measured amount of ink is deposited upon the surface of the printing plate (or printing cylinder) using an anilox roll. The print surface then rotates, contacting the print material which transfers the ink.

Originally flexo printing was basic in quality. Labels requiring high quality have generally been printed Offset until recently. In the last few years great advances have been made to the quality of flexo printing presses.

The greatest advances though have been in the area of PhotoPolymer Printing Plates, including improvements to the plate material and the method of plate creation. —usually photographic exposure followed by chemical etch, though also by direct laser engraving.

12- PHOTOCOPIER ( 1960s)

Xerographic office photocopying was introduced by Xerox in the 1960s, and over the following 20 years it gradually replaced copies made by Verifax, Photostat, carbon paper, mimeograph machines, and other duplicating machines. The prevalence of its use is one of the factors that prevented the development of the paperless office heralded early in the digital revolution.

13- THERMAL PRINTER

A thermal printer (or direct thermal printer) produces a printed image by selectively heating coated thermochromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated, producing an image.

14- LASER PRINTER ( 1969)

The laser printer, based on a modified xerographic copier, was invented at Xerox in 1969 by researcher Gary Starkweather, who had a fully functional networked printer system working by 1971. Laser printing eventually became a multibillion-dollar business for Xerox.

The first commercial implementation of a laser printer was the IBM model 3800 in 1976, used for high-volume printing of documents such as invoices and mailing labels. It is often cited as "taking up a whole room," implying that it was a primitive version of the later familiar device used with a personal computer. While large, it was designed for an entirely different purpose. Many 3800s are still in use.

The first laser printer designed for use with an individual computer was released with the Xerox Star 8010 in 1981. Although it was innovative, the Star was an expensive ($17,000) system that was only purchased by a small number of laboratories and institutions. After personal computers became more widespread, the first laser printer intended for a mass market was the HP LaserJet 8ppm, released in 1984, using a Canon engine controlled by HP software. The HP LaserJet printer was quickly followed by other laser printers from Brother Industries, IBM, and others.

Most noteworthy was the role the laser printer played in popularizing desktop publishing with the introduction of the Apple LaserWriter for the Apple Macintosh, along with Aldus PageMaker software, in 1985. With these products, users could create documents that would previously have required professional typesetting.

15- DOT MATRIX PRINTER ( 1970)

A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. Because the printing involves mechanical pressure, these printers can create carbon copies and carbonless copies.

Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either directly or through small levers (pawls). Facing the ribbon and the paper is a small guide plate (often made of an artificial jewel such as sapphire or ruby) pierced with holes to serve as guides for the pins. The moving portion of the printer is called the print head, and when running the printer as a generic text device generally prints one line of text at a time. Most dot matrix printers have a single vertical line of dot-making equipment on their print heads; others have a few interleaved rows in order to improve dot density.

16- INKJET PRINTERS

Inkjet printers are a type of computer printer that operates by propelling tiny droplets of liquid ink onto paper.

17- DYE-SUBLIMATION PRINTER

A dye-sublimation printer (or dye-sub printer) is a computer printer which employs a printing process that uses heat to transfer dye to a medium such as a plastic card, printer paper or poster paper. The process is usually to lay one color at a time using a ribbon that has color panels. Most dye-sublimation printers use CMYO colors which differs from the more recognised CMYK colors in that the black dye is eliminated in favour of a clear overcoating. This overcoating (which has numerous names depending on the manufacturer) is effectively a thin laminate which protects the print from discoloration from UV light and the air while also rendering the print water-resistant. Many consumer and professional dye-sublimation printers are designed and used for producing photographic prints.

18- DIGITAL PRESS ( 1993)

Digital printing is the reproduction of digital images on a physical surface, such as common or photographic paper or paperboard-cover stock, film, cloth, plastic, vinyl, magnets, labels etc.

It can be differentiated from litho, flexography, gravure or letterpress printing in many ways, some of which are;

Every impression made onto the paper can be different, as opposed to making several hundred or thousand impressions of the same image from one set of printing plates, as in traditional methods.

The Ink or Toner does not absorb into the substrate, as does conventional ink, but forms a layer on the surface and may be fused to the substrate by using an inline fuser fluid with heat process(toner) or UV curing process(ink).

It generally requires less waste in terms of chemicals used and paper wasted in set up or makeready(bringing the image "up to color" and checking position).

It is excellent for rapid prototyping, or small print runs which means that it is more accessible to a wider range of designers and more cost effective in short runs.

19- 3D PRINTING

Three-dimensional printing is a method of converting a virtual 3D model into a physical object. 3D printing is a category of rapid prototyping technology. 3D printers typically work by 'printing' successive layers on top of the previous to build up a three dimensional object. 3D printers are generally faster, more affordable and easier to use than other additive fabrication technologies.

20- TECHNOLOGICAL DEVELOPMENTS

20.1 Woodcut
Woodcut is a relief printing artistic technique in printmaking in which an image is carved into the surface of a block of wood, with the printing parts remaining level with the surface while the non-printing parts are removed, typically with gouges. The areas to show 'white' are cut away with a knife or chisel, leaving the characters or image to show in 'black' at the original surface level. The block is cut along the grain of the wood (unlike wood engraving where the block is cut in the end-grain). In Europe beechwood was most commonly used; in Japan, a special type of cherry wood was popular.

Woodcut first appeared in ancient China. From 6th century onward, woodcut icons became popular and especially flourished in Buddhist texts. Since the 10th century, woodcut pictures appeared in inbetweenings of Chinese literature, and some banknotes, such as Jiaozi (currency). Woodcut New Year picture are also very popular with the Chinese.

In China and Tibet printed images mostly remained tied as illustrations to accompanying text until the modern period. The earliest woodblock printed book, the Diamond Sutra contains a large image as frontispiece, and many Buddhist texts contain some images. Later some notable Chinese artists designed woodcuts for books, the individual print develop in China in the form of New Year picture as an art-form in the way it did in Europe and Japan.

In Europe, Woodcut is the oldest technique used for old master prints, developing about 1400, by using on paper existing techniques for printing on cloth. The explosion of sales of cheap woodcuts in the middle of the century led to a fall in standards, and many popular prints were very crude. The development of hatching followed on rather later than in engraving. Michael Wolgemut was significant in making German woodcut more sophisticated from about 1475, and Erhard Reuwich was the first to use cross-hatching (far harder to do than in engraving or etching). Both of these produced mainly book-illustrations, as did various Italian artists who were also raising standards there at the same period. At the end of the century Albrecht Dürer brought the Western woodcut to a level that has never been surpassed, and greatly increased the status of the single-leaf (ie an image sold separately) woodcut.

20.2- Engraving

Engraving is the practice of incising a design onto a hard, flat surface, by cutting grooves into it. The result may be a decorated object in itself, as when silver, gold or steel are engraved, or may provide an intaglio printing plate, of copper or another metal, for printing images on paper, which are called engravings. Engraving was a historically important method of producing images on paper, both in artistic printmaking, and also for commercial reproductions and illustrations for books and magazines. It has long been replaced by photography in its commercial applications and, partly because of the difficulty of learning the technique, is much less common in printmaking, where it has been largely replaced by etching and other techniques. Other terms often used for engravings are copper-plate engraving and Line engraving. These should all mean exactly the same, but especially in the past were often used very loosely to cover several printmaking techniques, so that many so-called engravings were in fact produced by totally different techniques, such as etching.

In antiquity, the only engraving that could be carried out is evident in the shallow grooves found in some jewellery after the beginning of the 1st Millennium B.C. The majority of so-called engraved designs on ancient gold rings or other items were produced by chasing or sometimes a combination of lost-wax casting and chasing.

In the European Middle Ages goldsmiths used engraving to decorate and inscribe metalwork. It is thought that they began to print impressions of their designs to record them. From this grew the engraving of copper printing plates to produce artistic images on paper, known as old master prints in Germany in the 1430s. Italy soon followed. Many early engravers came from a goldsmithing background. The first and greatest period of the engraving was from about 1470 to 1530, with such masters as Martin Schongauer , Albrecht Dürer , and Lucas van Leiden.

20.3- Etching

Etching is the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal (the original process—in modern manufacturing other chemicals may be used on other types of material). As an intaglio method of printmaking it is, along with engraving, the most important technique for old master prints, and remains widely used today.

20.4- Halftoning

Halftone is the reprographic technique that simulates continuous tone imagery through the use of equally spaced dots of varying size. 'Halftone' can also be used to refer specifically to the image that is produced by this process.

The idea of halftone printing originates from William Fox Talbot. In the early 1850s he suggested using "photographic screens or veils" in connection with a photographic intaglio process.

Several different kinds of screens were proposed during the following decades, but the first half-tone photo-engraving process was invented by Canadians George-Édouard Desbarats and William Leggo Jr. On October 30, 1869, Desbarats published the Canadian Illustrated News which became the world’s first periodical to successfully employ this photo-mechanical technique; featuring a full page half-tone image of His Royal Highness Prince Arthur, from a photograph by Notman. Ambitious to exploit a much larger circulation, Debarats and Leggo went to New York and launched the New York Daily Graphic in March 1873, which became the world’s first illustrated daily.

The first truly successful commercial method was patented by Frederic Ives of Philadelphia in 1881. But although he found a way of breaking up the image into dots of varying sizes he did not make use of a ===screen===. In 1882 the German George Meisenbach patented a halftone process in England. His invention was based on the previous ideas of Berchtold and Swan. He used single lined screens which were turned during exposure to produce cross-lined effects. He was the first to achieve any commercial success with relief halftones.

20.5- Xerography

Xerography (or electrophotography) is a photocopying technique developed by Chester Carlson in 1938 and patented on October 6, 1942.

In 1937 Bulgarian physicist Georgi Nadjakov found that when placed into electric field and exposed to light, some dielectrics acquire permanent electric polarization in the exposed areas. That polarization persists in the dark and is destroyed in light. Chester Carlson, the inventor of photocopying, was originally a patent attorney and part-time researcher and inventor. His job at the patent office in New York required him to make a large number of copies of important papers. Carlson, who was arthritic, found this a painful and tedious process. This prompted him to conduct experiments with photoconductivity. Carlson experimented with "electrophotography" in his kitchen and in 1938, applied for a patent for the process. He made the first "photocopy" using a zinc plate covered with sulfur. The words "10-22-38 Astoria" were written on a microscope slide, which was placed on top of more sulfur and under a bright light. After the slide was removed, a mirror image of the words remained. Carlson tried to sell his invention to some companies, but because the process was still underdeveloped he failed. At the time multiple copies were made using carbon paper or duplicating machines and people did not feel the need for an electronic machine. Between 1939 and 1944, Carlson was turned down by over 20 companies, including IBM and GE, neither of which believed there was a significant market for copiers.

17) HEWLETT PACKARD "HP" PRINTERS

2009-06-19T15:31:00.000-07:00

The Hewlett-Packard Company, commonly referred to as HP, is a technology corporation headquartered in Palo Alto, California, United States. HP is the largest technology company in the world and operates in nearly every country. HP specializes in developing and manufacturing computing, storage, and networking hardware, software and services. Major product lines include personal computing devices, enterprise servers, related storage devices, as well as a diverse range of printers and other imaging products. Other product lines, including electronic test equipment and systems, medical electronic equipment, solid state components and instrumentation for chemical analysis were spun off as Agilent Technologies in 1999.

HP markets its products to households, small to medium size businesses and enterprises both directly, via online distribution, consumer-electronics and office-supply retailers, software partners and major technology vendors.

HP posted US $91.7 billion in annual revenue in 2006 compared to US$91.4 billion for IBM, making it the world's largest technology vendor in terms of sales. In 2007 the revenue was $104 billion, making HP the first IT company in history to report revenues exceeding $100 billion.

HP is the largest worldwide seller of personal computers, surpassing rival Dell, according to market research firms Gartner and IDC reported in January 2008; the gap between HP and Dell widened substantially at the end of 2007, with HP taking a near 3.9% market share lead. HP is also the 5th largest software company in the world. It is one of the only American PC-focused computer companies publicly traded under the New York Stock Exchange.

1- COMPANY HISTORY

1.1- Founding

William (Bill) Hewlett and David (Dave) Packard both graduated in electrical engineering from Stanford University in 1935. The company originated in a garage in nearby Palo Alto during a fellowship they had with a past professor, Frederick Terman at Stanford during the Great Depression. Terman was considered a mentor to them in forming Hewlett-Packard.

The partnership was formalized in 1939 with an investment of US$538. Hewlett and Packard tossed a coin to decide whether the company they founded would be called Hewlett-Packard or Packard-Hewlett. Packard won the coin toss but named their electronics manufacturing enterprise the "Hewlett-Packard Company". HP incorporated on August 18, 1947, and went public on November 6, 1957.

Of the many projects they worked on, their very first financially successful product was a precision audio oscillator, the Model HP200A. Their innovation was the use of a small light bulb as a temperature dependent resistor in a critical portion of the circuit. This allowed them to sell the Model 200A for $54.40 when competitors were selling less stable oscillators for over $200. The Model 200 series of generators continued until at least 1972 as the 200AB, still tube-based but improved in design through the years. At 33 years, it was perhaps the longest-selling basic electronic design of all time.

One of the company's earliest customers was The Walt Disney Company, which bought eight Model 200B oscillators (at $71.50 each) for use in certifying the Fantasound surround sound systems installed in theaters for the movie Fantasia.

1.2- Early years
The company was originally rather unfocused, working on a wide range of electronic products for industry and even agriculture. Eventually they elected to focus on high-quality electronic test and measurement equipment.

From the 1940s until well into the 1990s the company concentrated on making electronic test equipment – signal generators, voltmeters, oscilloscopes, frequency counters, thermometers, time standards, wave analyzers, and many other instruments. A distinguishing feature was pushing the limits of measurement range and accuracy; many HP instruments were more sensitive, accurate, and precise than other comparable equipment.

Following the pattern set by the company's first product, the 200A, test instruments were labelled with three to five digits followed by the letter "A". Improved versions went to suffixes "B" through "E". As the product range grew wider HP started using product designators starting with a letter for accessories, supplies, software, and components.

1.3- The 1960s
HP is recognized as the symbolic founder of Silicon Valley, although it did not actively investigate semiconductor devices until a few years after the "Traitorous Eight" had abandoned William Shockley to create Fairchild Semiconductor in 1957. Hewlett-Packard's HP Associates division, established around 1960, developed semiconductor devices primarily for internal use. Instruments and calculators were some of the products using these devices.

HP partnered in the 1960s with Sony and the Yokogawa Electric companies in Japan to develop several high-quality products. The products were not a huge success, as there were high costs in building HP-looking products in Japan. HP and Yokogawa formed a joint venture (Yokogawa-Hewlett-Packard) in 1963 to market HP products in Japan. HP bought Yokogawa Electric's share of Hewlett-Packard Japan in 1999.

HP spun off a small company, Dynec, to specialize in digital equipment. The name was picked so that the HP logo "hp" could be turned upside down to be the logo "dy" of the new company. Eventually Dynec changed to Dymec, then was folded back into HP. HP experimented with using Digital Equipment Corporation minicomputers with its instruments. But after deciding that it would be easier to buy another small design team than deal with DEC, HP entered the computer market in 1966 with the HP 2100 / HP 1000 series of minicomputers. These had a simple accumulator-based design, with registers arranged somewhat similarly to the Intel x86 architecture still used today. The series was produced for 20 years, in spite of several attempts to replace it, and was a forerunner of the HP 9800 and HP 250 series of desktop and business computers.

1.4- The 1970s
The HP 3000 was an advanced stack-based design for a business computing server, later redesigned with RISC technology, that has only recently been retired from the market. The HP 2640 series of smart and intelligent terminals introduced forms-based interfaces to ASCII terminals, and also introduced screen labeled function keys, now commonly used on gas pumps and bank ATMs. Although scoffed at in the formative days of computing, HP would eventually surpass even IBM as the world's largest technology vendor in sales.

HP is identified by Wired magazine as the producer of the world's first marketed, mass-produced personal computer, the Hewlett-Packard 9100A, introduced in 1968. HP called it a desktop calculator because, as Bill Hewlett said, "If we had called it a computer, it would have been rejected by our customers' computer gurus because it didn't look like an IBM. We therefore decided to call it a calculator, and all such nonsense disappeared." An engineering triumph at the time, the logic circuit was produced without any integrated circuits; the assembly of the CPU having been entirely executed in discrete components. With CRT display, magnetic-card storage, and printer, the price was around $5000. The machine's keyboard was a cross between that of a scientific calculator and an adding machine. There was no alphabetical keyboard.

Steve Wozniak, co-founder of Apple, originally designed the Apple I computer while working at HP and offered it to them under their right of first refusal to his work, but they did not take it up as the company wanted to stay in scientific, business, and industrial markets.

The company earned global respect for a variety of products. They introduced the world's first handheld scientific electronic calculator in 1972 (the HP-35), the first handheld programmable in 1974 (the HP-65), the first alphanumeric, programmable, expandable in 1979 (the HP-41C), and the first symbolic and graphing calculator, the HP-28C. Like their scientific and business calculators, their oscilloscopes, logic analyzers, and other measurement instruments have a reputation for sturdiness and usability (the latter products are now part of spin-off Agilent's product line). The company's design philosophy in this period was summarized as "design for the guy at the next bench".

The 98x5 series of technical desktop computers started in 1975 with the 9815, and the cheaper 80 series, again of technical computers, started in 1979 with the 85. These machines used a version of the BASIC programming language which was available immediately after they were switched on, and used a proprietary magnetic tape for storage. HP computers were similar in capabilities to the much later IBM Personal Computer, although the limitations of available technology forced prices to be high.

1.5- The 1980s
In 1984, HP introduced both inkjet and laser printers for the desktop. Along with its scanner product line, these have later been developed into successful multifunction products, the most significant being single-unit printer/scanner/copier/fax machines. The print mechanisms in HP's tremendously popular LaserJet line of laser printers depend almost entirely on Canon's components (print engines), which in turn use technology developed by Xerox. HP develops the hardware, firmware, and software that convert data into dots for the mechanism to print.

In 1987, the Palo Alto garage where Hewlett and Packard started their business was designated as a California State historical landmark.

1.6- The 1990s

In the 1990s, HP expanded their computer product line, which initially had been targeted at university, research, and business customers, to reach consumers.

HP also grew through acquisitions, buying Apollo Computer in 1989 and Convex Computer in 1995.

Later in the decade HP opened hpshopping.com as an independent subsidiary to sell online, direct to consumers; in 2005 the store was renamed "HP Home & Home Office Store."

In 1999, all of the businesses not related to computers, storage, and imaging were spun off from HP to form Agilent. Agilent's spin-off was the largest initial public offering in the history of Silicon Valley. The spin-off created an $8 billion company with about 30,000 employees, manufacturing scientific instruments, semiconductors, optical networking devices, and electronic test equipment for telecom and wireless R&D and production.

In July 1999, HP appointed Carly Fiorina as CEO, the first female CEO of a company in the Dow Jones Industrial Average. Fiorina served as CEO during the tech downtown of the turn of the 2nd millenium. During her tenure, the market halved HP’s value commensurate with other tech companies at the time and the company incurred heavy job losses. The HP Board of Directors asked Fiorina to step down in 2005, and she resigned on February 9, 2005.

1.7- 2000 and beyond

Compaq merger. HP merged with Compaq in 2002. Compaq itself had bought Tandem Computers in 1997 (which had been started by ex-HP employees), and Digital Equipment Corporation in 1998. Following this strategy HP became a major player in desktops, laptops, and servers for many different markets. After the merger with Compaq, the new ticker symbol became "HPQ", a combination of the two previous symbols, "HWP" and "CPQ", to show the significance of the alliance. In 2006 hp outsourced its enterprise support to countries with lower cost workers: the Spanish support (for Spain) moved to Slovakia, the German support moved to Bulgaria, English support moved to Costa Rica, and so on.

EDS purchase. On May 13, 2008, HP and Electronic Data Systems announced [13] that they had signed a definitive agreement under which HP would purchase EDS. On June 30, HP announced that the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 had expired. "The transaction still requires EDS stockholder approval and regulatory clearance from the European Commission and other non-U.S. jurisdictions and is subject to the satisfaction or waiver of the other closing conditions specified in the merger agreement." The agreement was finalized on August 26, 2008 and it was publicly announced that EDS would be re-branded "EDS an HP company."

HP also expanded its presence in Israel first with the acqusistion in 2002 of Indigo Digital Press and in November 2005 with the acquisition of Scitex Vision from Scitex Corporation Ltd..

In October 2008, Hewlett-Packard (Canada) Co. was named one of "Canada's Top 100 Employers" by Mediacorp Canada Inc., and was featured in Maclean's newsmagazine. Later that month, Hewlett-Packard (Canada) Co. was also named one of Greater Toronto's Top Employers, which was announced by the Toronto Star newspaper.

2- TECHNOLOGY & PRODUCTS

HP has successful lines of printers, scanners, digital cameras, calculators, PDAs, servers, workstation computers, and computers for home and small business use computers; many of the computers came from the 2002 merger with Compaq. HP today promotes itself as supplying not just hardware and software, but also a full range of services to design, implement and support IT infrastructure.

The three business segments: Enterprise Storage and Servers (ESS), HP Services (HPS), and HP Software are structured beneath the broader Technology Solutions Group (TSG).

2.1- Imaging and Printing Group (IPG)

According to HP's 2005 U.S. SEC 10-K filing, HP's Imaging and Printing Group is "the leading imaging and printing systems provider in the world for printer hardware, printing supplies and scanning devices, providing solutions across customer segments from individual consumers to small and medium businesses to large enterprises." This division is currently headed by Vyomesh Joshi.

Products and technology associated with the Imaging and Printing Group include:

Inkjet and LaserJet printers, consumables and related products

Officejet all-in-one multifunction printer/scanner/faxes

Large Format Printers

Indigo Digital Press

HP Web Jetadmin printer management software

HP Output Management suite of software, including HP Output Server

LightScribe optical recording technology that laser-etches labels on disks

HP Photosmart digital cameras and photo printers

HP SPaM Hosted within IPG, SPaM is an internal consulting group that supports all HP businesses on mission-critical strategic and operation decisions.

On December 23, 2008, HP releases iPrint Photo for iPhone a free downloadable

software application that allows to print 4" x 6" photo.

2.2- Personal Systems Group (PSG)
HP's Personal Systems Group claims to be "one of the leading vendors of personal computers ("PCs") in the world based on unit volume shipped and annual revenue."[16]

Personal Systems Group products/technology include:

Business PCs and accessories

Consumer PCs and accessories including the HP Pavilion, Compaq Presario and VoodooPC series

Workstations for Unix, Windows and Linux systems

Handheld Computing including iPAQ Pocket PC handheld computing devices (from Compaq)

Digital "Connected" Entertainment including HP MediaSmart TVs, HP MediaSmart
Servers, HP MediaVaults, and DVD+RW drives. HP resold the Apple iPod until November 2005.

Home Storage Servers

2.3- Technology Solutions Group (TSG)

TSG incorporates Technical services, EDS, HP Software, Enterprise Storage and Servers Group (ESS) and ProCurve Networking.

2.4- Office of Strategy and Technology
HP's Office of Strategy and Technology, under Executive Vice President Shane Robison:

Steers the company's $3.6 billion research and development investment — including HP Labs.

Fosters the development of the company's global technical community.

Leads the company's strategy and corporate development efforts — including mergers, acquisitions, divestitures, intellectual property licensing, venture capital partnerships, and the ProCurve Networking Business Unit.

Performs worldwide corporate marketing activities — including external and internal communications, brand marketing, customer intelligence, and corporate affairs.

3- ENVIRONMENTAL RECORD
In 1998, the United States Environmental Protection Agency‎ sought a $2.5 million penalty against Hewlett Packard for violations against the Substance Control Act. The PA EPA alleged that the company had not filed a Pre-Manufacturing Notice (PMN) before it began manufacturing and exporting chemicals. Without filing these PMNs, the EPA cannot conduct risk analysis of new chemicals.

In 2002, Scorecard.org ranked Hewlett Packard facilities in the top 10-20 percentile for total environmental releases and top 30-40 percentile for air releases of recognized developmental toxicants. It also showed that HPs factory in Puerto Rico released 246 lb (112 kg) of air released TRI pollutants, and had a total of 483,136 lb (219,147 kg) of production related wastes.

In July 2007, the company announced that it had met its target, set in 2004, to recycle 1 billion pounds of electronics and toner and ink cartridges. It has set a new goal of recycling a further 2 billion pounds of hardware by the end of 2010. In 2006, the company recovered 187 million pounds of electronics, 73 percent more than its closest competitor.

4- HP CERTIFIED PROFESSIONALS
Hewlett-Packard's Certified Professional (HP-CP) program was developed to confirm the technical skills, sales competencies and knowledge that is required to propose and deploy, service and support technology and solutions sold by HP. HP-CP is intended for customers, resellers, and HP employees.

5- SPONSORSHIPS
HP has many sponsorships. One well known sponsorship is of Walt Disney World's Epcot Park's Mission: SPACE. Others can be found on Hewlett-Packard's website . From 1995 to 1999 they were the shirt sponsor of English Premier League club Tottenham Hotspur. They also sponsored the BMW Williams Formula 1 team. Hewlett-Packard also has the naming rights arrangement for the HP Pavilion at San Jose, home of the San Jose Sharks NHL hockey team.

6- PRODUCT LEGACY
Agilent Technologies, not HP, retains the direct product legacy of the original company founded in 1939. Agilent's current portfolio of electronic instruments are descended from HP's very earliest products. HP entered the computer business only after its instrumentation competencies were well-established.

After the acquisition of Compaq in 2002, HP has maintained the "Compaq Presario" brand on low-end home desktops and laptops, the "HP Compaq" brand on business desktops and laptops, and the "HP ProLiant" brand on Intel-architecture servers. (The "HP Pavilion" brand is used on home entertainment laptops and all home desktops.)

HP uses DEC's "StorageWorks" brand on storage systems; Tandem's "NonStop" servers are now branded as "HP Integrity NonStop".

16) LASER PRINTERS

2009-06-19T15:24:00.000-07:00

A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers (MFPs), laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor.

1- OVERVIEW

A laser beam projects an image of the page to be printed onto an electrically charged rotating drum coated with selenium. Photoconductivity removes charge from the areas exposed to light. Dry ink (toner) particles are then electrostatically picked up by the drum's charged areas. The drum then prints the image onto paper by direct contact and heat, which fuses the ink to the paper.

Laser printers have many significant advantages over other types of printers. Unlike impact printers, laser printer speed can vary widely, and depends on many factors, including the graphic intensity of the job being processed. The fastest models can print over 200 monochrome pages per minute (12,000 pages per hour). The fastest color laser printers can print over 100 pages per minute (6000 pages per hour). Very high-speed laser printers are used for mass mailings of personalized documents, such as credit card or utility bills, and are competing with lithography in some commercial applications.

The cost of this technology depends on a combination of factors, including the cost of paper, toner, and infrequent drum replacement, as well as the replacement of other consumables such as the fuser assembly and transfer assembly. Often printers with soft plastic drums can have a very high cost of ownership that does not become apparent until the drum requires replacement.

A duplexing printer (one that prints on both sides of the paper) can halve paper costs and reduce filing volumes. Formerly only available on high-end printers, duplexers are now common on mid-range office printers, though not all printers can accommodate a duplexing unit. Duplexing can also give a slower page-printing speed, because of the longer paper path.

In comparison with the laser printer, most inkjet printers and dot-matrix printers simply take an incoming stream of data and directly imprint it in a slow lurching process that may include pauses as the printer waits for more data. A laser printer is unable to work this way because such a large amount of data needs to output to the printing device in a rapid, continuous process. The printer cannot stop the mechanism precisely enough to wait until more data arrives, without creating a visible gap or misalignment of the dots on the printed page.

Instead the image data is built up and stored in a large bank of memory capable of representing every dot on the page. The requirement to store all dots in memory before printing has traditionally limited laser printers to small fixed paper sizes such as letter or A4. Most laser printers are unable to print continuous banners spanning a sheet of paper two meters long, because there is not enough memory available in the printer to store such a large image before printing begins.

2- HISTORY
The laser printer was invented at Xerox in 1969 by researcher Gary Starkweather, who had an improved printer working by 1971 and incorporated into a fully functional networked printer system by about a year later. The prototype was built by modifying an existing xerographic copier. Starkweather disabled the imaging system and created a spinning drum with 8 mirrored sides, with a laser focused on the drum. Light from the laser would bounce off the spinning drum, sweeping across the page as it traveled through the copier. The hardware was completed in just a week or two, but the computer interface and software took almost 3 months to complete.

The first commercial implementation of a laser printer was the IBM model 3800 in 1976, used for high-volume printing of documents such as invoices and mailing labels. It is often cited as "taking up a whole room," implying that it was a primitive version of the later familiar device used with a personal computer. While large, it was designed for an entirely different purpose. Many 3800s are still in use.[citation needed]

The first laser printer designed for use with an individual computer was released with the Xerox Star 8010 in 1981. Although it was innovative, the Star was an expensive ($17,000) system that was purchased by only a relatively small number of businesses and institutions. After personal computers became more widespread, the first laser printer intended for a mass market was the HP LaserJet 8ppm, released in 1984, using a Canon engine controlled by HP software. The HP LaserJet printer was quickly followed by laser printers from Brother Industries, IBM, and others.

As with most electronic devices, the cost of laser printers has fallen markedly over the years. In 1984, the HP LaserJet sold for $3500[3], had trouble with even small, low resolution graphics, and weighed 71 pounds (32 kg). Low end monochrome laser printers often sell for less than $75 as of 2008. These printers tend to lack onboard processing and rely on the host computer to generate a raster image (see Winprinter), but still will outperform the LaserJet Classic in nearly all situations.

3- HOW IT WORKS

There are typically seven steps involved in the laser printing process:

3.1- Raster image processing

Each horizontal strip of dots across the page is known as a raster line or scan line. Creating the image to be printed is done by a Raster Image Processor (RIP), typically built into the laser printer. The source material may be encoded in any number of special page description languages such as Adobe PostScript (PS) , HP Printer Command Language (PCL), or Microsoft XML Page Specification (XPS) , as well as unformatted text-only data. The RIP uses the page description language to generate a bitmap of the final page in the raster memory. Once the entire page has been rendered in raster memory, the printer is ready to begin the process of sending the rasterized stream of dots to the paper in a continuous stream.

3.2- Charging

A corona wire (in older printers) or a primary charge roller projects an electrostatic charge onto the photoreceptor (otherwise named the photoconductor unit), a revolving photosensitive drum or belt, which is capable of holding an electrostatic charge on its surface while it is in the dark.

Numerous patents describe the photosensitive drum coating as a silicon sandwich with a photocharging layer, a charge leakage barrier layer, as well as a surface layer. One version uses amorphous silicon containing hydrogen as the light receiving layer, Boron nitride as a charge leakage barrier layer, as well as a surface layer of doped silicon, notably silicon with oxygen or nitrogen which at sufficient concentration resembles machining silicon nitride; the effect is that of a light chargeable diode with minimal leakage and a resistance to scuffing.

3.3- Exposing

The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system of lenses and mirrors onto the photoreceptor. The beam sweeps across the photoreceptor at an angle to make the sweep straight across the page; the cylinder continues to rotate during the sweep and the angle of sweep compensates for this motion. The stream of rasterized data held in memory turns the laser on and off to form the dots on the cylinder. (Some printers switch an array of light emitting diodes spanning the width of the page, but these devices are not "Laser Printers".) Lasers are used because they generate a narrow beam over great distances. The laser beam neutralizes (or reverses) the charge on the white parts of the image, leaving a static electric negative image on the photoreceptor surface to lift the toner particles.

3.4- Developing
The surface with the latent image is exposed to toner, fine particles of dry plastic powder mixed with carbon black or coloring agents. The charged toner particles are given a negative charge, and are electrostatically attracted to the photoreceptor where the laser wrote the latent image. Because like charges repel, the negatively charged toner will not touch the drum where light has not removed the negative charge.

The overall darkness of the printed image is controlled by the high voltage charge applied to the supply toner. Once the charged toner has jumped the gap to the surface of the drum, the negative charge on the toner itself repels the supply toner and prevents more toner from jumping to the drum. If the voltage is low, only a thin coat of toner is needed to stop more toner from transferring. If the voltage is high, then a thin coating on the drum is too weak to stop more toner from transferring to the drum. More supply toner will continue to jump to the drum until the charges on the drum are again high enough to repel the supply toner. At the darkest settings the supply toner voltage is high enough that it will also start coating the drum where the initial unwritten drum charge is still present, and will give the entire page a dark shadow.

3.5- Transferring
The photoreceptor is pressed or rolled over paper, transferring the image. Higher-end machines use a positively charged transfer roller on the back side of the paper to pull the toner from the photoreceptor to the paper.

3.6- Fusing

The paper passes through rollers in the fuser assembly where heat and pressure (up to 200 Celsius) bond the plastic powder to the paper.
One roller is usually a hollow tube (heat roller) and the other is a rubber backing roller (pressure roller). A radiant heat lamp is suspended in the center of the hollow tube, and its infrared energy uniformly heats the roller from the inside. For proper bonding of the toner, the fuser roller must be uniformly hot.

The fuser accounts for up to 90% of a printer's power usage. The heat from the fuser assembly can damage other parts of the printer, so it is often ventilated by fans to move the heat away from the interior. The primary power saving feature of most copiers and laser printers is to turn off the fuser and let it cool. Resuming normal operation requires waiting for the fuser to return to operating temperature before printing can begin.

Some printers use a very thin flexible metal fuser roller, so there is less mass to be heated and the fuser can more quickly reach operating temperature. This both speeds printing from an idle state and permits the fuser to turn off more frequently to conserve power.

If paper moves through the fuser more slowly, there is more roller contact time for the toner to melt, and the fuser can operate at a lower temperature. Smaller, inexpensive laser printers typically print slowly, due to this energy-saving design, compared to large high speed printers where paper moves more rapidly through a high-temperature fuser with a very short contact time.

3.7- Cleaning
When the print is complete, an electrically neutral soft plastic blade cleans any excess toner from the photoreceptor and deposits it into a waste reservoir, and a discharge lamp removes the remaining charge from the photoreceptor.

Toner may occasionally be left on the photoreceptor when unexpected events such as a paper jam occur. The toner is on the photoconductor ready to apply, but the operation failed before it could be applied. The toner must be wiped off and the process restarted.

Waste toner cannot be reused for printing because it can be contaminated with dust and paper fibers. A quality printed image requires pure, clean toner. Reusing contaminated toner can result in splotchy printed areas or poor fusing of the toner into the paper. There are some exceptions however, most notably some Brother and Toshiba laser printers, which use a patented method to clean and recycle the waste toner.

3.8- Multiple steps occurring at once
Once the raster image generation is complete all steps of the printing process can occur one after the other in rapid succession. This permits the use of a very small and compact unit, where the photoreceptor is charged, rotates a few degrees and is scanned, rotates a few more degrees and is developed, and so forth. The entire process can be completed before the drum completes one revolution.

Different printers implement these steps in distinct ways. Some "laser" printers actually use a linear array of light-emitting diodes to "write" the light on the drum (see LED printer). The toner is based on either wax or plastic, so that when the paper passes through the fuser assembly, the particles of toner melt. The paper may or may not be oppositely charged. The fuser can be an infrared oven, a heated pressure roller, or (on some very fast, expensive printers) a xenon flash lamp. The Warm Up process that a laser printer goes through when power is initially applied to the printer consists mainly of heating the fuser element. Many printers have a toner-conservation mode, called "Economode" by Hewlett-Packard, which uses about half as much toner but produces a lighter draft-quality output.

4- COLOR LASER PRINTERS
Color laser printers use colored toner (dry ink), typically cyan, magenta, yellow, and black (CMYK), with a printing pass for each toner color.

Color adds complexity to the printing process because very slight misalignments known as registration errors can occur between printing each color, causing unintended color fringing, blurring, or light/dark streaking along the edges of colored regions. To permit a high registration accuracy, some color laser printers use a large belt the size of a full sheet of paper to generate the image. All three or four layers of toner are precisely applied to the belt, and the combined layers are then applied to the paper in a single step.

Color laser printers typically require four times as much memory as a monochrome printer to print the same size document, because each of the three CMY or four CMYK color separations needs to be rasterized and stored in memory before printing can begin.

5- DPI RESOLUTIONS

1200 DPI printers are commonly available during 2008.

2400 DPI electrophotographic printing plate makers, essentially laser printers that print on plastic sheets, are also available.

6- LASER PRINTER MAINTENANCE

Most consumer and small business laser printers use a cartridge that combines the photoreceptor (sometimes called "photoconductor unit") with the supply toner and waste toner bottles and various wiper blades. When the supply toner is consumed, replacing the cartridge automatically replaces the photoreceptor, waste toner bottle, and blades.

Some small consumer printers use a separate toner bottle that can be replaced several times separately from the photoreceptor, allowing for a much lower cost of operation. High-volume business laser printers separate all components into individual modules.

After printing about fifty thousand pages, typical maintenance is to vacuum the mechanism, and clean or replace the paper handling rollers. The rollers have a thick rubber coating, which eventually suffers wear and becomes covered with slippery paper dust. They can usually be cleaned with a damp lint-free rag and there are chemical solutions that can help restore the traction of the rubber.

After one hundred thousand pages, it is common for the fuser assembly to either wear out or need replacing. The fuser heating rollers are often coated with an oil that prevents toner from sticking to the rollers. A small amount of the oil coating is absorbed by each piece of paper passing through the fuser, eventually requiring the oil supply to be replenished or the pressure roller assembly to be completely replaced. It is common for the fuser assembly to be left unmaintained until the toner starts sticking to the rollers, which creates a repeating ragged line on every printed page due to the rollers not being smooth anymore.

Color laser printers are typically more expensive and higher maintenance than monochrome laser printers since they contain more imaging components. Color laser printers intended for high volume use may require supplies that monochrome printers do not use, while the least expensive consumer color laser printers are expected to wear out and fail four times faster during color printing, compared to monochrome printing.

Due to current market incentives, the least expensive consumer color laser printers often cost less than the total value of the replacement parts inside the printer. The photoreceptor assembly for example may last 100,000 pages but may cost as much to replace as buying a new printer with new toner cartridges included.

7- SAFETY HAZARDS, HEALTH RISKS, & PRECAUTION

7.1- Shock hazards
Although modern printers include many safety interlocks and protection circuits, it is possible for a high voltage or a residual voltage to be present on the various rollers, wires, and metal contacts inside a laser printer. Care should be taken to avoid unnecessary contact with these parts to reduce the potential for painful electrical shock.

7.2- Toner clean-up
Toner particles are designed to have electrostatic properties and can develop static-electric charges when they rub against other particles, objects, or the interiors of transport systems and vacuum hoses. Because of this and its small particle size, toner should not be vacuumed with a conventional home vacuum cleaner. Static discharge from charged toner particles can ignite dust in the vacuum cleaner bag or create a small explosion if sufficient toner is airborne. This may damage the vacuum cleaner or start a fire. In addition, toner particles are so fine that they are poorly filtered by conventional household vacuum cleaner filter bags and blow through the motor or back into the room.

Toner particles melt (or fuse) when warmed. Small toner spills can be wiped up with a cold, damp cloth.

If toner spills into the laser printer, a special type of vacuum cleaner with an electrically conductive hose and a high efficiency (HEPA) filter may be needed for effective cleaning. These are called ESD-safe (Electrostatic Discharge-safe) or toner vacuums. Similar HEPA-filter equipped vacuums should be used for clean-up of larger toner spills.

Toner is easily cleaned from most water-washable clothing. As toner is a wax or plastic powder with a low melting temperature, it must be kept cold during the cleaning process. Washing a toner stained garment in cold water is often successful. Even warm water is likely to result in permanent staining. The washing machine should be filled with cold water before adding the garment. Washing through two cycles improves the chances of success. The first may use hand wash dish detergent, with the second cycle using regular laundry detergent. Residual toner floating in the rinse water of the first cycle will remain in the garment and may cause a permanent graying. A clothes dryer or iron should not be used until it is certain that all the toner has been removed.

7.3- Ozone hazards
As a natural part of the printing process, the high voltages inside the printer can produce a corona discharge that generates a small amount of ionized oxygen and nitrogen, forming ozone and nitrogen oxides. In larger commercial printers and copiers, a carbon filter in the air exhaust stream breaks down these oxides to prevent pollution of the office environment.

However, some ozone escapes the filtering process in commercial printers, and ozone filters are not used in many smaller consumer printers. When a laser printer or copier is operated for a long period of time in a small, poorly ventilated space, these gases can build up to levels at which the odor of ozone or irritation may be noticed. A potential for creating a health hazard is theoretically possible in extreme cases.

7.4- Respiratory health risks
According to a recent study conducted in Queensland, Australia, some printers emit sub-micrometre particles which some suspect may be associated with respiratory diseases. Of 63 printers evaluated in the Queensland University of Technology study, 17 of the strongest emitters were made by Hewlett-Packard and one by Toshiba. The machine population studied, however, was only those machines already in place in the building and was thus biased toward specific manufacturers. The authors noted that particle emissions varied substantially even among the same model of machine. According to Professor Morawska of Queensland University, one printer emitted as many particles as a burning cigarette.

"The health effects from inhaling ultrafine particles depend on particle composition, but the results can range from respiratory irritation to more severe illness such as cardiovascular problems or cancer." (Queensland University of Technology).
A 2006 study in Japan found that laser printers increase concentrations of styrene, xylenes, and ozone, and that ink-jet printers emitted pentanol.

Muhle et al. (1991) reported that the responses to chronically inhaled copying toner, a plastic dust pigmented with carbon black, titanium dioxide and silica were also similar qualitatively to titanium dioxide and diesel exhaust.

15) PRINTERS ( COMPUTING)

2009-06-19T15:18:00.000-07:00

In computing, a printer is a peripheral which produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most newer printers, a USB cable to a computer which serves as a document source. Some printers, commonly known as network printers, have built-in network interfaces (typically wireless or Ethernet), and can serve as a hardcopy device for any user on the network. Individual printers are often designed to support both local and network connected users at the same time.

In addition, a few modern printers can directly interface to electronic media such as memory sticks or memory cards, or to image capture devices such as digital cameras, scanners; some printers are combined with a scanners and/or fax machines in a single unit, and can function as photocopiers. Printers that include non-printing features are sometimes called Multifunction Printers (MFP), Multi-Function Devices (MFD), or All-In-One (AIO) printers. Most MFPs include printing, scanning, and copying among their features. A Virtual printer is a piece of computer software whose user interface and API resemble that of a printer driver, but which is not connected with a physical computer printer.

Printers are designed for low-volume, short-turnaround print jobs; requiring virtually no setup time to achieve a hard copy of a given document. However, printers are generally slow devices (30 pages per minute is considered fast; and many inexpensive consumer printers are far slower than that), and the cost per page is actually relatively high. The printing press remains the machine of choice for high-volume, professional publishing. However, as printers have improved in quality and performance, many jobs which used to be done by professional print shops are now done by users on local printers; see desktop publishing. The world's first computer printer was a 19th century mechanically driven apparatus invented by Charles Babbage for his Difference Engine.

1- PRINTING TECHNOLOGY
Printers are routinely classified by the underlying print technology they employ; numerous such technologies have been developed over the years. The choice of print engine has a substantial effect on what jobs a printer is suitable for, as different technologies are capable of different levels of image/text quality, print speed, low cost, noise; in addition, some technologies are inappropriate for certain types of physical media (such as carbon paper or transparencies).

Another aspect of printer technology that is often forgotten is resistance to alteration: liquid ink such as from an inkjet head or fabric ribbon becomes absorbed by the paper fibers, so documents printed with a liquid ink sublimation printer are more difficult to alter than documents printed with toner or solid inks, which do not penetrate below the paper surface.

Checks should either be printed with liquid ink or on special "check paper with toner anchorage". For similar reasons carbon film ribbons for IBM Selectric typewriters bore labels warning against using them to type negotiable instruments such as checks. The machine-readable lower portion of a check, however, must be printed using MICR toner or ink. Banks and other clearing houses employ automation equipment that relies on the magnetic flux from these specially printed characters to function properly.

2- MODERN PRINT-TECHNOLOGY

The following printing technologies are routinely found in modern printers,

2.1- Toner-based printers

Toner-based printers work using the Xerographic principle that is used in most photocopiers: by adhering toner to a light-sensitive print drum, then using static electricity to transfer the toner to the printing medium to which it is fused with heat and pressure.

The most common type of toner-based printer is the laser printer, which uses precision lasers to cause toner adherence. Laser printers are known for high quality prints, good print speed, and a low (Black and White) cost-per-copy. They are the most common printer for many general-purpose office applications, but are much less common as consumer printers due to their high initial cost - although this cost is dropping.

Laser printers are available in both color and monochrome varieties.

Another toner based printer is the LED printer which uses an array of LEDs instead of a laser to cause toner adhesion to the print drum.

Recent research has also indicated that Laser printers emit potentially dangerous ultrafine particles, possibly causing health problems associated with respiration and cause pollution equivalent to cigarettes. The degree of particle emissions varies with age, model and design of each printer but is generally proportional to the amount of toner required. Furthermore, a well ventilated workspace would allow such ultrafine particles to disperse thus reducing the health side effects.

2.2- Liquid inkjet printers

Inkjet printers operate by propelling variably-sized droplets of liquid or molten material (ink) onto almost any sized page. They are the most common type of computer printer for the general consumer due to their low cost, high quality of output, capability of printing in vivid color, and ease of use.

2.3- Solid ink printers
Solid Ink printers, also known as phase-change printers, are a type of thermal transfer printer. They use solid sticks of CMYK colored ink (similar in consistency to candle wax), which are melted and fed into a piezo crystal operated print-head. The printhead sprays the ink on a rotating, oil coated drum. The paper then passes over the print drum, at which time the image is transferred, or transfixed, to the page.

Solid ink printers are most commonly used as color office printers, and are excellent at printing on transparencies and other non-porous media. Solid ink printers can produce excellent results. Acquisition and operating costs are similar to laser printers. Drawbacks of the technology include high power consumption and long warm-up times from a cold state.

Also, some users complain that the resulting prints are difficult to write on (the wax tends to repel inks from pens), and are difficult to feed through Automatic Document Feeders, but these traits have been significantly reduced in later models. In addition, this type of printer is only available from one manufacturer, Xerox, manufactured as part of their Xerox Phaser office printer line. Previously, solid ink printers were manufactured by Tektronix, but Tek sold the printing business to Xerox in 2001.

2.4- Dye-sublimation printers
A dye-sublimation printer (or dye-sub printer) is a printer which employs a printing process that uses heat to transfer dye to a medium such as a plastic card, paper or canvas. The process is usually to lay one color at a time using a ribbon that has color panels. Dye-sub printers are intended primarily for high-quality color applications, including color photography; and are less well-suited for text. While once the province of high-end print shops, dye-sublimation printers are now increasingly used as dedicated consumer photo printers.

2.5- Inkless printers
2.5.1 - Thermal printers work by selectively heating regions of special heat-sensitive paper. Monochrome thermal printers are used in cash registers, ATMs, gasoline dispensers and some older inexpensive fax machines. Colors can be achieved with special papers and different temperatures and heating rates for different colors. One example is the ZINK technology.

2.5.2- UV printersXerox is working on an inkless printer which will use a special reusable paper coated with a few micrometres of UV light sensitive chemicals. The printer will use a special UV light bar which will be able to write and erase the paper. As of early 2007 this technology is still in development and the text on the printed pages can only last between 16-24 hours before fading.

3- OBSOLETE & SPECIAL PURPOSE PRINTING TECHNOLOGIES
The following technologies are either obsolete, or limited to special applications though most were, at one time, in widespread use.

Impact printers rely on a forcible impact to transfer ink to the media, similar to the action of a typewriter. All but the dot matrix printer rely on the use of formed characters, letterforms that represent each of the characters that the printer was capable of printing. In addition, most of these printers were limited to monochrome printing in a single typeface at one time, although bolding and underlining of text could be done by overstriking, that is, printing two or more impressions in the same character position. Impact printers varieties include, Typewriter-derived printers, Teletypewriter-derived printers, Daisy wheel printers, Dot matrix printers and Line printers. Dot matrix printers remain in common use in businesses where multi-part forms are printed, such as car rental service counters. An overview of impact printing contains a detailed description of many of the technologies used.

Pen-based plotters were an alternate printing technology once common in engineering and architectural firms. Pen-based plotters rely on contact with the paper (but not impact, per se), and special purpose pens that are mechanically run over the paper to create text and images.

3.1- Typewriter-derived printers
Several different computer printers were simply computer-controllable versions of existing electric typewriters. The Friden Flexowriter and IBM Selectric typewriter were the most-common examples. The Flexowriter printed with a conventional typebar mechanism while the Selectric used IBM's well-known "golf ball" printing mechanism. In either case, the letter form then struck a ribbon which was pressed against the paper, printing one character at a time. The maximum speed of the Selectric printer (the faster of the two) was 15.5 characters per second.

3.2- Teletypewriter-derived printers
The common teleprinter could easily be interfaced to the computer and became very popular except for those computers manufactured by IBM. Some models used a "typebox" that was positioned (in the X- and Y-axes) by a mechanism and the selected letter from was struck by a hammer. Others used a type cylinder in a similar way as the Selectric typewriters used their type ball. In either case, the letter form then struck a ribbon to print the letterform. Most teleprinters operated at ten characters per second although a few achieved 15 CPS.

3.3- Daisy wheel printers
Daisy-wheel printers operate in much the same fashion as a typewriter. A hammer strikes a wheel with petals (the daisy wheel), each petal containing a letter form at its tip. The letter form strikes a ribbon of ink, depositing the ink on the page and thus printing a character. By rotating the daisy wheel, different characters are selected for printing.

These printers were also referred to as letter-quality printers because, during their heyday, they could produce text which was as clear and crisp as a typewriter (though they were nowhere near the quality of printing presses). The fastest letter-quality printers printed at 30 characters per second.

3.4- Dot-matrix printers
In the general sense many printers rely on a matrix of pixels, or dots, that together form the larger image. However, the term dot matrix printer is specifically used for impact printers that use a matrix of small pins to create precise dots. The advantage of dot-matrix over other impact printers is that they can produce graphical images in addition to text; however the text is generally of poorer quality than impact printers that use letterforms (type).

A Tandy 1000 HX with a Tandy DMP-133 dot-matrix printer

Dot-matrix printers can be broadly divided into two major classes:

Ballistic wire printers (discussed in the dot matrix printers article)
Stored energy printers
Dot matrix printers can either be character-based or line-based (that is, a single horizontal series of pixels across the page), referring to the configuration of the print head.

At one time, dot matrix printers were one of the more common types of printers used for general use - such as for home and small office use. Such printers would have either 9 or 24 pins on the print head. 24-pin print heads were able to print at a higher quality. Once the price of inkjet printers dropped to the point where they were competitive with dot matrix printers, dot matrix printers began to fall out of favor for general use.

Some dot matrix printers, such as the NEC P6300, can be upgraded to print in color. This is achieved through the use of a four-color ribbon mounted on a mechanism (provided in an upgrade kit that replaces the standard black ribbon mechanism after installation) that raises and lowers the ribbons as needed. Color graphics are generally printed in four passes at standard resolution, thus slowing down printing considerably. As a result, color graphics can take up to four times longer to print than standard monochrome graphics, or up to 8-16 times as long at high resolution mode.

Dot matrix printers are still commonly used in low-cost, low-quality applications like cash registers, or in demanding, very high volume applications like invoice printing. The fact that they use an impact printing method allows them to be used to print multi-part documents using carbonless copy paper (like sales invoices and credit card receipts), whereas other printing methods are unusable with paper of this type. Dot-matrix printers are now (as of 2005) rapidly being superseded even as receipt printers.

3.5- Line printers
Line printers, as the name implies, print an entire line of text at a time. Three principal designs existed. In drum printers, a drum carries the entire character set of the printer repeated in each column that is to be printed. In chain printers (also known as train printers), the character set is arranged multiple times around a chain that travels horizontally past the print line. In either case, to print a line, precisely timed hammers strike against the back of the paper at the exact moment that the correct character to be printed is passing in front of the paper. The paper presses forward against a ribbon which then presses against the character form and the impression of the character form is printed onto the paper.

Comb printers represent the third major design. These printers were a hybrid of dot matrix printing and line printing. In these printers, a comb of hammers printed a portion of a row of pixels at one time (for example, every eighth pixel). By shifting the comb back and forth slightly, the entire pixel row could be printed (continuing the example, in just eight cycles). The paper then advanced and the next pixel row was printed. Because far less motion was involved than in a conventional dot matrix printer, these printers were very fast compared to dot matrix printers and were competitive in speed with formed-character line printers while also being able to print dot-matrix graphics.

Line printers were the fastest of all impact printers and were used for bulk printing in large computer centres. They were virtually never used with personal computers and have now been replaced by high-speed laser printers.

The legacy of line printers lives on in many computer operating systems, which use the abbreviations "lp", "lpr", or "LPT" to refer to printers.

3.6- Pen-based plotters
A plotter is a vector graphics printing device which operates by moving a pen over the surface of paper. Plotters have been (and still are) used in applications such as computer-aided design, though they are being replaced with wide-format conventional printers (which nowadays have sufficient resolution to render high-quality vector graphics using a rasterized print engine). It is commonplace to refer to such wide-format printers as "plotters", even though such usage is technically incorrect.

4 - OTHER PRINTERS
A number of other sorts of printers are important for historical reasons, or for special purpose uses:

Digital minilab (photographic paper)

Electrolytic printers

Microsphere (special paper)

Spark printer

barcode printer multiple technologies, including: thermal printing, inkjet printing, and laser printing barcodes

Billboard / sign paint spray printers

Laser etching (product packaging) industrial printers.

5- PRINTING MODE
The data received by a printer may be:

1.a string of characters
2.a bitmapped image
3.a vector image
Some printers can process all three types of data, others not.

Character Printers (such as Daisy wheel printers) can handle only plain text data or rather simple point plots.

Pen Plotters typically process vector images. Inkjet based Plotters can adequately reproduce all three.

Modern printing technology, such as laser printers and inkjet printers, can adequately reproduce all three. This is especially true of printers equipped with support for PostScript and/or PCL; which includes the vast majority of printers produced today.

Today it is common to print everything (even plain text) by sending ready bitmapped images to the printer, because it allows better control over formatting. Many printer drivers do not use the text mode at all, even if the printer is capable of it.

6- MONOCHROME, COLOR & PHOTO PRINTERS
A monochrome printer can only produce an image consisting of one color, usually black. A monochrome printer may also be able to produce various tones of that color, such as a grey-scale.

A color printer can produce images of multiple colors.

A photo printer is a color printer that can produce images that mimic the color range (gamut) and resolution of photographic methods of printing. Many can be used autonomously (without a computer), with a memory card or USB connector.

7- THE PRINTERS MANUFACTURING BUSINESS
Often the razor and blades business model is applied. That is, a company may sell a printer at cost, and make profits on the ink cartridge, paper, or some other replacement part. This has caused legal disputes regarding the right of companies other than the printer manufacturer to sell compatible ink cartridges.

8- PRINTING SPEED
The speed of early printers was measured in units of characters per second. More modern printers are measured in pages per minute. These measures are used primarily as a marketing tool, and are not well standardised. Usually pages per minute refers to sparse monochrome office documents, rather than dense pictures which usually print much more slowly. PPM are most of the time referring to A4 paper in Europe and letter paper in the US, resulting in a 5-10% difference.

14) HISTORY OF VIDEO GAMES

2009-06-19T15:07:00.000-07:00

Video games were introduced as a commercial entertainment medium in 1971, becoming the basis for a new entertainment industry in the late 1970s/early 1980s in the United States, Japan, and Europe. After a disastrous industry collapse in 1983 and a subsequent rebirth two years later, the video game industry has experienced sustained growth for over two decades to become a $11 billion industry, which rivals the motion picture industry as the most profitable entertainment industry in the world.

Origins

A device called the Cathode-Ray Tube Amusement Device was patented in the United States by Thomas T. Goldsmith Jr. and Estle Ray Mann. The patent was filed on January 25, 1947 and issued on December 14, 1948. It described using eight vacuum tubes to simulate a missile firing at a target and contains knobs to adjust the curve and speed of the missile. Because computer graphics could not be drawn electronically at the time, small targets were drawn on a simple overlay and placed on the screen.

In 1949-1950, Charly Adama created a "Bouncing Ball" program for MIT's Whirlwind computer. While the program was not yet interactive, it was a precursor to games soon to come.

In February 1951, Christopher Strachey tried to run a draughts programme he had written for the NPL Pilot ACE. The program exceeded the memory capacity of the machine and by October, Strachey had recoded his program for a machine at Manchester with a larger memory capacity.

OXO, a graphical version of tic-tac-toe, was created by A.S. Douglas in 1952 at the University of Cambridge, in order to demonstrate his thesis on human-computer interaction. It was developed on the EDSAC computer, which uses a cathode ray tube displaying memory contents as a visual display. The player competes against the computer.

1950s–1960s

The majority of early computer games ran on university mainframe computers in the United States and were developed by individuals as a hobby. The limited accessibility of early computer hardware meant that these games were small in number and forgotten by posterity.

In 1959-1961, a collection of interactive graphical programs were created on the TX-0 machine at MIT:

Mouse in the Maze: which allowed users to place maze walls, bits of cheese, and (in some versions) glasses of martini by way of a light pen interacting with the screen. One could then release the mouse and watch it traverse the maze to find the goodies.
HAX: By adjusting two switches on the console, various graphical displays and sounds could be made.

Tic-Tac-Toe: Using the light pen, the user could play a simple game of naughts and crosses against the computer.
In 1961, a group of students at MIT, including Steve Russell, programmed a game titled Spacewar! on the DEC PDP-1, a new computer at the time. The game pitted two human players against each other, each controlling a spacecraft capable of firing missiles, while a black hole in the center of the screen created a large hazard for the crafts. The game was eventually distributed with new DEC computers and traded throughout the then-primitive internet. Spacewar! is credited as the first influential computer game.

In 1966, Ralph Baer created a simple video game named Corndog that displayed on a standard television set, the first to do so. With the assistance of Baer, Bill Harrison created the light gun and developed several video games with Bill Rusch in 1967. Ralph Baer continued development, and in 1968 a prototype was completed that could run several different games such as table tennis and target shooting.

In 1969, AT&T computer programmer Ken Thompson wrote a game called Space Travel for the MULTICS operating system. This game simulated various bodies of the solar system and their movements and the player could attempt to land a spacecraft on them. AT&T pulled out of the MULTICS project, and Thompson ported the game to FORTRAN code running on the GECOS operating system of the General Electric GE 635 mainframe computer. Runs on this system cost about $75 per hour, and Thompson looked for a smaller, less expensive computer to use. He found an underused PDP-7, and he and Dennis Ritchie started porting the game to PDP-7 assembly language. In the process of learning to develop software for the machine, the development process of the UNIX operating system began, and Space Travel has been called the first UNIX application.

In 1958 William Higinbotham created a game using an oscilloscope and analog computer. Aptly titled Tennis for Two, it was used to entertain visitors of the Brookhaven National Laboratory in New York. Tennis for Two showed a simplified tennis court from the side, featuring a gravity-controlled ball that needed to be played over the "net," unlike its successors. The game was played with two box-shaped controllers, both equipped with a knob for trajectory, and a button for hitting the ball. Tennis for Two was exhibited for two seasons before its dismantlement in 1959.

1970s
At this time, computer and video game development split to many areas, such as arcade machines, university computers, handhelds, and home computers.

Golden age of video arcade games
In September 1971, the Galaxy Game was installed at a student union at Stanford University. Based on Spacewar!, this was the first coin-operated video game. Only one was built, using a DEC PDP-11/20 and vector display terminals. In 1972 it was expanded to be able to handle four to eight consoles.

Also in 1971, Nolan Bushnell and Ted Dabney created a coin-operated arcade version of Spacewar! and called it Computer Space. Nutting Associates bought the game and manufactured 1,500 Computer Space machines, with the release taking place in November 1971. The game was unsuccessful due to its long learning-curve, but was a landmark, being the first mass-produced video game and the first offered for commercial sale.

Bushnell and Dabney felt they did not receive enough earnings by licensing Computer Space to Nutting Associates. Atari was founded in 1972. The first arcade video game with widespread success was Atari's PONG, released the same year. The game is loosely based on table tennis: a ball is "served" from the center of the court and as the ball moves towards their side of the court each player must manoeuvre their bat to hit the ball back to their opponent. Atari sold 19,000 PONG machines, creating many imitators.

The arcade game industry entered its Golden Age in 1978 with the release of Space Invaders by Taito, a success that inspired dozens of manufacturers to enter the market. In 1979, Atari released Asteroids. Color arcade games became more popular in 1979 and 1980 with the arrival of titles such as Pac-Man. The Golden Age saw a prevalence of arcade machines in malls, traditional storefronts, restaurants and convenience stores.

Dawn of Console Gaming (First Generation)

1972 saw the launch of console based videogames with the original Magnavox Odyssey system in the USA. This had no gaming cartridges, but only a few programmed games in the console. The games featured a plastic sheet overlay, that was placed on the television picture tube and held by static electricity, which would define the gaming space such as a basketball court or tennis court.

Philips bought Magnavox and released a different game in Europe in using the Odyssey brand in 1974 and an evolved game that Magnavox had been developing for the US market. In all the Odyssey system achieved sales of 2 million units.

University mainframe computers
University mainframe game development blossomed in the early 1970s. There is little record of all but the most popular games, as they were not marketed, or regarded as a serious endeavor. The people, generally students, writing these games often were doing so illicitly, making questionable use of very expensive computing resources, and thus were not anxious to let very many people know what they were doing. There were, however, at least two notable distribution paths for the student game designers of this time.

The PLATO system was an educational computing environment designed at the University of Illinois and which ran on mainframes made by Control Data Corporation. Games were often exchanged between different PLATO systems.

DECUS was the user group for computers made by Digital Equipment Corporation (DEC), and distributed programs, including games, that would run on the various types of DEC computers.

A number of noteworthy games were also written for Hewlett Packard minicomputers such as the HP2000.

Highlights of this period, in approximate chronological order, include:

1971: Don Daglow wrote the first computer baseball game on a DEC PDP-10 mainframe at Pomona College. Players could manage individual games or simulate an entire season. Daglow went on to team with programmer Eddie Dombrower to design Earl Weaver Baseball, published by Electronic Arts in 1987.

1971: Star Trek was created, probably by Mike Mayfield on a Sigma 7 minicomputer at MIT. This is the best-known and most widely played of the 1970s Star Trek titles, and was played on a series of small "maps" of galactic sectors printed on paper or on the screen. It was the first major game to be ported across hardware platforms by students. Daglow also wrote a popular Star Trek game for the PDP-10 during 1971–1972, which presented the action as a script spoken by the TV program's characters. A number of other Star Trek themed games were also available via PLATO and DECUS throughout the decade.

1972: Gregory Yob wrote Hunt the Wumpus for the PDP-10, a hide-and-seek game, though it could be considered the first text adventure. Yob wrote it in reaction to existing hide-and-seek games such as Hurkle, Mugwump (game), and Snark.
1974: Both Maze War (on the Imlac PDS-1 at the NASA Ames Research Center in California) and Spasim (on PLATO) appeared, pioneering examples of early multi-player 3D first person shooters.

1974: Brad Fortner and others developed Airfight as an educational flight simulator. To make it more interesting, all players shared an airspace flying their choice of military jets, loaded as desired with weapons, fuel and the desire to shoot down other players. Despite mediocre graphics and slow screen refresh, it became a popular game on the PLATO system. Airfight was the inspiration for what became the Microsoft Flight Simulator.

1975: Will Crowther wrote the first text adventure game as we would recognize it today, Adventure (originally called ADVENT, and later Colossal Cave). It was programmed in Fortran for the PDP-10. The player controls the game through simple sentence-like text commands and receives descriptive text as output. The game was later re-created by students on PLATO, so it is one of the few titles that became part of both the PLATO and PDP-10 traditions.

1975: Before the mid-1970s games typically communicated to the player on paper, using teletype machines or a line printer, at speeds ranging from 10 to 30 characters per second with a rat-a-tat-tat sound as a metal ball or belt with characters was pressed against the paper through an inked ribbon by a hammer. By 1975, many universities had discarded these terminals for CRT screens, which could display thirty lines of text in a few seconds instead of the minute or more that printing on paper required. This led to the development of a series of games that drew "graphics" on the screen.

1975: Daglow, then a student at Claremont Graduate University, wrote the first Computer role playing game on PDP-10 mainframes, Dungeon. The game was an unlicensed implementation of the new role playing game Dungeons & Dragons. Although displayed in text, it was the first game to use line of sight graphics, top-down dungeon maps that showed the areas that the party had seen or could see, allowing for light or darkness, the different vision of elves and dwarves, etc.

1975: At about the same time the RPG dnd, also based on Dungeons and Dragons first appeared on PLATO system CDC computers. For players in these schools dnd, not Dungeon, was the first computer role-playing game.

1977: Kelton Flinn and John Taylor create the first version of Air, a text air combat game that foreshadowed their later work creating the first-ever graphical online multi-player game, Air Warrior. They would found the first successful online game company, Kesmai, now part of Electronic Arts. As Flinn has said: "If Air Warrior was a primate swinging in the trees, AIR was the text-based amoeba crawling on the ocean floor. But it was quasi-real time, multi-player, and attempted to render 3-D on the terminal using ASCII graphics. It was an acquired taste."

1977: The writing of the original Zork was started by Dave Lebling, Marc Blank, Tim Anderson, and Bruce Daniels. Unlike Crowther, Daglow and Yob, the Zork team recognized the potential to move these games to the new personal computers, and they founded text adventure publisher Infocom in 1979. The company was later sold to Activision. In a classic case of "connections", Lebling was a member of the same D&D group as Will Crowther, but not at the same time. Lebling has been quoted as saying "I think I actually replaced him when he dropped out. Zork was 'derived' from Advent in that we played Advent … and tried to do a 'better' one. There was no code borrowed … and we didn’t meet either Crowther or Woods until much later."

1980: Michael Toy, Glenn Wichman and Ken Arnold released Rogue on BSD Unix after two years of work, inspiring many roguelike games ever since. Like Dungeon on the PDP-10 and dnd on PLATO, Rogue displayed dungeon maps using text characters. Unlike those games, however, the dungeon was randomly generated for each play session, so the path to treasure and the enemies who protected it were different for each game. As the Zork team had done, Rogue was adapted for home computers and became a commercial product.

Home computers

Soon many of these games (at first clones of mainframe classics such as Star Trek, and then later clones of popular arcade games) were being distributed through a variety of channels, such as printing the game’s source code in books (such as David Ahl’s BASIC Computer Games), magazines (Creative Computing), and newsletters, which allowed users to type in the code for themselves. Early game designers like Crowther, Daglow and Yob would find the computer code for their games—which they had never thought to copyright—published in books and magazines, with their names removed from the listing. Early home computers from Apple, Commodore, Tandy and others had many games that people typed in.

Another distribution channel was the physical mailing and selling of floppy disks, cassette tapes and ROM cartridges. Soon a small cottage industry was formed, with amateur programmers selling disks in plastic bags put on the shelves of local shops, or sent through the mail. Richard Garriott distributed several copies of his 1980 computer role-playing game Akalabeth: World of Doom in plastic bags before the game was published.

1977
In 1977, manufacturers of older obsolete consoles and Pong clones sold their systems at a loss to clear stock, creating a glut in the market and causing Fairchild and RCA to abandon their game consoles. Only Atari and Magnavox stayed in the home console market.

" SECOND GENERATION (1976–1980)"
In the earliest consoles, the computer code for one or more games was hardcoded into microchips using discrete logic, and no additional games could ever be added. By the mid-1970s video games were found on cartridges. Programs were burned onto ROM chips that were mounted inside plastic cartridge casings that could be plugged into slots on the console. When the cartridges were plugged in, the general-purpose microprocessors in the consoles read the cartridge memory and ran whatever program was stored there. Rather than being confined to a small selection of games included in the box, consumers could now amass libraries of game cartridges. The first of these consoles to use the ROM cartridge format was the Fairchild 'Video Entertainment System (VES), released in 1976.

Three machines dominated the second generation of consoles in North America, far outselling their rivals:

In 1977, Atari released its ROM cartridge based console called the Video Computer System (VCS), later called Atari 2600. Nine games were designed and released for the holiday season. It would quickly become by far the most popular of all the early consoles.
Intellivision, introduced by Mattel in 1980. Though chronologically part of what is called the "8-bit era", the Intellivision had a unique processor with instructions that were 10 bits wide (allowing more instruction variety and potential speed), and registers 16 bits wide. The system, which featured graphics superior to the older Atari 2600, rocketed to popularity.
ColecoVision, an even more powerful machine, appeared in 1982. Its sales also took off, but the presence of three major consoles in the marketplace and a glut of poor quality games began to overcrowd retail shelves and erode consumers' interest in video games. Within a year this overcrowded market would crash.
In 1979, Activision was created by disgruntled former Atari programmers. It was the first third-party developer of video games.

1980s
In the early 1980s, the computer gaming industry experienced its first major growing pains. Publishing houses appeared, with many honest businesses (and in rare cases such as Electronic Arts, successfully surviving to this day) alongside fly-by-night operations that cheated the games' developers. While some early 80s games were simple clones of existing arcade titles, the relatively low publishing costs for personal computer games allowed for many bold, unique games, a legacy that continues to this day. The primary gaming computers of the 1980s emerged in 1982: the Commodore 64, Apple II (although the Apple II started in 1977) and Sinclair ZX Spectrum. The ZX Spectrum was mostly used and known only in the UK, whilst the USA had the Apple II, Commodore 64, and Atari 800. Over the run of 15 years, the Apple II had a total of almost 20,000 programs, making it the 8-bit computer with the most software overall.

The Golden Age of Arcade Games reached its full steam in the 1980s, with many technically innovative and genre-defining games in the first few years of the decade. Defender (1980) established the scrolling shooter and was the first to have events taking place outside the player’s view, displayed by a radar view showing a map of the whole playfield. Battlezone (1980) used wireframe vector graphics to create the first true three-dimensional game world. 3D Monster Maze (1981) was the first 3D game for a home computer, while Dungeons of Daggorath (1982) added various weapons and monsters, sophisticated sound effects, and a "heartbeat" health monitor. Pole Position (1982) used sprite-based, pseudo-3D graphics when it pioneered the "rear-view racer format" where the player’s view is behind and above the vehicle, looking forward along the road with the horizon in sight. The style would remain in wide use even after true 3D graphics became standard for racing games. Pac-Man (1980) was the first game to achieve widespread popularity in mainstream culture and the first game character to be popular in his own right. Dragon's Lair (1983) was the first laserdisc game, and introduced full-motion video to video games. Journey Escape, a videogame developed by Data Age for the Atari 2600 console, and released in 1982, stars the rock band Journey, one of the world's most popular acts at the time, and is based on their album of the same name.

With Adventure establishing the genre, the release of Zork in 1980 further popularized text adventure games in home computers and established developer Infocom’s dominance in the field. As these early computers often lacked graphical capabilities, text adventures proved successful. When affordable computers started catching up to and surpassing the graphics of consoles in the late 1980s, the pure text adventure's popularity waned in favor of graphic adventures and other genres. The text adventure would eventually be known as interactive fiction and a small dedicated following has kept the genre going, with new releases being nearly all free.

Also published in 1980 was Roberta Williams' Mystery House, for the Apple II. It was the first graphic adventure on home computers. Graphics consisted entirely of static monochrome drawings, and the interface still used the typed commands of text adventures. It proved very popular at the time, and she and husband Ken went on to found Sierra On-Line, a major producer of adventure games. Mystery House remains largely forgotten today.

In August 1982, the Commodore 64 was released to the public. It found initial success because it was marketed and priced aggressively. It had a BASIC programming environment and advanced graphic and sound capabilities for its time, similar to the ColecoVision console. It also utilized the same game controller ports popularized by the Atari 2600, allowing gamers to use their old joysticks with the system. It would become the most popular home computer of its day in the USA and many other countries and the best-selling single computer model of all time internationally.

At around the same time, the Sinclair ZX Spectrum was released in the United Kingdom and quickly became the most popular home computer in many areas of Western Europe, and later the Eastern bloc due to the ease with which clones could be produced.

SuperSet Software created Snipes, a text-mode networked computer game in 1983 to test a new IBM Personal Computer based computer network and demonstrate its capabilities. Snipes is officially credited as being the original inspiration for Novell NetWare. It is believed to be the first network game ever written for a commercial personal computer and is recognized alongside 1974’s Maze War (a networked multiplayer maze game for several research machines) and Spasim (a 3D multiplayer space simulation for time shared mainframes) as the precursor to multiplayer games such as 1987's MIDI Maze, and Doom in 1993.

The true modern adventure game would be born with the Sierra King's Quest series in 1984. It featured color graphics and a third person perspective. An on-screen player-controlled character could be moved behind and in front of objects on a 2D background drawn in perspective, creating the illusion of pseudo-3D space. Commands were still entered via text. LucasArts would do away with this last vestige feature of text adventures when its 1987 adventure Maniac Mansion built with its SCUMM system allowed a point-and-click interface. Sierra and other game companies quickly followed with their own mouse-driven games.

With Elite in 1984, David Braben and Ian Bell ushered in the age of modern style 3D graphics, creating a game with convincing vector worlds, full 6 degree freedom of movement, and thousands of visitable planetary systems. Initially only available for the BBC Micro and Acorn Electron, the success of this title caused it eventually to be ported to all popular formats, including the Commodore 64, Sinclair ZX Spectrum, Commodore Amiga, Atari ST and even the Nintendo Entertainment System, although this version only received a European release.

The IBM PC compatible computer became a technically competitive gaming platform with IBM’s PC/AT in 1984. The new 16-color EGA display standard allowed its graphics to approach the quality seen in popular home computers like the Commodore 64. The primitive 4-color CGA graphics of previous models had limited the PC’s appeal to the business segment, since its graphics failed to compete with the C64 or Apple II. The sound capabilities of the AT, however, were still limited to the PC speaker, which was substandard compared to the built-in sound chips used in many home computers. Also, the relatively high cost of the PC compatible systems severely limited their popularity in gaming.

The Apple Macintosh also arrived at this time. It lacked the color capabilities of the earlier Apple II, instead preferring a much higher pixel resolution, but the operating system support for the GUI attracted developers of some interesting games (e.g. Lode Runner) even before color returned in 1987 with the Mac II.

In computer gaming, the later 1980s are primarily the story of the United Kingdom’s rise to prominence. The market in the UK was primely positioned for this task: personal computer users were offered a smooth scale of power versus price, from the Sinclair ZX Spectrum up to the Amiga; developers and publishers were in close enough proximity to offer each other support; and the NES made much less of an impact than it did in the United States, due to the enormous popularity of personal computers there, even though it outsold all the other home consoles (such as the Sega Master System)

The arrival of the Atari ST and Commodore Amiga in 1985 was the beginning of a new era of 16-bit machines. For many users they were too expensive until later on in the decade, at which point advances in the IBM PC’s open platform had caused the IBM PC compatibles to become comparably powerful at a lower cost than their competitors. The VGA standard developed for IBM’s new PS/2 line in 1987 gave the PC the potential for 256-color graphics. This was a big jump ahead of most 8-bit home computers but still lagging behind platforms with built-in sound and graphics hardware like the Amiga, causing an odd trend around '89-91 towards developing to a seemingly inferior machine. Thus while both the ST and Amiga were host to many technically excellent games, their time of prominence proved to be shorter than that of the 8-bit machines, which saw new ports well into the 80s and even the 90s.

Dedicated sound cards started to address the issue of poor sound capabilities in IBM PC compatibles in the late 1980s. AdLib set an early de facto standard for sound cards in 1987, with its card based on the Yamaha YM3812 sound chip. This would last until the introduction of Creative Labs' Sound Blaster in 1989, which took the chip and added new features while remaining compatible with AdLib cards, and creating a new de facto standard. However, many games would still support these and rarer things like the Roland MT-32 and Disney Sound Source into the early 90s. The initial high cost of sound cards meant they would not find widespread use until the 1990s.

Shareware gaming first appeared in the mid 1980s, but its big successes came in the 1990s.

Early online gaming
Dialup bulletin board systems were popular in the 1980s, and sometimes used for online game playing. The earliest such systems, in the late 1970s and early 1980s, had a crude plain-text interface, but later systems made use of terminal-control codes (the so-called ANSI art, which included the use of IBM-PC-specific characters not actually part of an ANSI standard) to get a pseudo-graphical interface. Some BBSes offered access to various games which were playable through such an interface, ranging from text adventures to gambling games like blackjack (generally played for "points" rather than real money). On multiuser BBSs (where more than one person could be online at once), there were sometimes games allowing the different users to interact with one another; some such games of the fantasy role-playing variety were known as MUDs, for "multi-user dungeons". These games eventually evolved into what are known today as MMORPG.

Commercial online services also arose during this decade, starting with a plain-text interface similar to BBSs (but operated on large mainframe computers permitting larger numbers of users to be online at once), and moving by the end of the decade to fully-graphical environments using software specific to each personal computer platform. Popular text-based services included CompuServe, The Source, and GEnie, while platform-specific graphical services included PlayNET and Quantum Link for the Commodore 64, AppleLink for the Apple II and Macintosh, and PC Link for the IBM PC, all of which were run by the company which eventually became America Online; and a competing service, Prodigy. Interactive games were a feature of these services, though until 1987 they used text-based displays, not graphics.

Handheld LCD games
Nintendo's Game & Watch line began in 1980. The success of these LCD handhelds spurred dozens of other game and toy companies to make their own portable games, many being copies of Game & Watch titles or adaptations of popular arcade games. Improving LCD technology meant the new handhelds could be more reliable and consume less batteries than LED or VFD games, most only needing watch batteries. They could also be made much smaller than most LED handhelds, even small enough to wear on one’s wrist like a watch. Tiger Electronics borrowed this concept of videogaming with cheap, affordable handhelds and still produces games in this model to the present day.

Video game crash of 1983
At the end of 1983, the industry experienced losses more severe than the 1977 crash. This was the "crash" of the video game industry, as well as the bankruptcy of several companies that produced North American home computers and video game consoles from late 1983 to early 1984. It brought an end to what is considered to be the second generation of console video gaming. Causes of the crash include the production of poorly designed games such as E.T. the Extra-Terrestrial and Pac-Man for the Atari 2600 that suffered due to extremely tight deadlines. It was discovered that more Pac-Man cartridges were manufactured than there were systems made. In addition, so many E.T. the Extra-Terrestrial cartridges were left unsold that Atari allegedly buried thousands of cartridges in a landfill in New Mexico.

" THIRD GENERATION(1984–1994) "
In 1984, the computer gaming market took over from the console market following the crash of that year; computers offered equal gaming ability and since their simple design allowed games to take complete command of the hardware after power-on, they were nearly as simple to start playing with as consoles.

In 1985, the North American video game console market was revived with Nintendo’s release of its 8-bit console, the Famicom, known outside Asia as Nintendo Entertainment System (NES). It was bundled with Super Mario Bros. and instantly became a success. The NES dominated the North American and the Japanese market until the rise of the next generation of consoles in the early 1990s. Other markets were not as heavily dominated, allowing other consoles to find an audience like the Sega Master System in Europe, Australia and Brazil (though it was sold in North America as well).

In the new consoles, the gamepad took over joysticks, paddles, and keypads as the default game controller included with the system. The gamepad design of an 8 direction Directional-pad (or D-pad for short) with 2 or more action buttons became the standard.

The Legend of Zelda series made its debut in 1986 with The Legend of Zelda. Around the same time, the Dragon Quest series debuted with Dragon Quest (1986), and has created a phenomenon in Japanese culture ever since. Shortly thereafter, the Japanese company Square was struggling and Hironobu Sakaguchi decided to make his final game, titled Final Fantasy (1987), a role-playing game (RPG) modeled after Dragon Quest, and the Final Fantasy series was born as a result. Final Fantasy would later go on to become the most successful RPG franchise. Hideo Kojima’s Metal Gear series also made its debut with the release of Metal Gear (1987) on the MSX2 computer, giving birth to the stealth game genre. Metal Gear was ported to the NES shortly after. In 1989, Capcom released Sweet Home (1989) on the NES, which served as a precursor to the survival horror genre.

In 1988, Nintendo published their first issue of Nintendo Power magazine.

1990s
The video game industry matured into a mainstream form of entertainment in the 1990s. Major developments of the 1990s included the beginning of a larger consolidation of publishers, higher budget games, increased size of production teams and collaborations with both the music and motion picture industries. Examples of this would be Mark Hamill's involvement with Wing Commander III or Quincy Jones' introduction of QSound.

The increasing computing power and decreasing cost of processors as the Intel 80386, Intel 80486, and the Motorola 68030, caused the rise of 3D graphics, as well as "multimedia" capabilities through sound cards and CD-ROMs. Early 3D games began with flat-shaded graphics (Elite, Starglider 2 or Alpha Waves[10] ), and then simple forms of texture mapping (Wolfenstein 3D).

In the early 1990s, shareware distribution was a popular method of publishing games for smaller developers, including then-fledgling companies such as Apogee (now 3D Realms), Epic Megagames (now Epic Games), and id Software. It gave consumers the chance to try a trial portion of the game, usually restricted to the game’s complete first section or "episode", before purchasing the rest of the adventure. Racks of games on single 5 1/4" and later 3.5" floppy disks were common in many stores, often only costing a few dollars each. Since the shareware versions were essentially free, the cost only needed to cover the disk and minimal packaging. As the increasing size of games in the mid-90s made them impractical to fit on floppies, and retail publishers and developers began to earnestly mimic the practice, shareware games were replaced by shorter demos (often only one or two levels), distributed free on CDs with gaming magazines and over the Internet.

In 1992 the game Dune II was released. It was by no means the first in the genre (several other games can be called the very first real-time strategy game, see the History of RTS), but it set the standard game mechanics for later blockbuster RTS games such as Warcraft: Orcs & Humans, Command & Conquer, and StarCraft. The RTS is characterized by an overhead view, a "mini-map", and the control of both the economic and military aspects of an army. The rivalry between the two styles of RTS play—Warcraft style, which used GUIs accessed once a building was selected, and C&C style, which allowed construction of any unit from within a permanently visible menu—continued into the start of the next millennium.

Alone in the Dark (1992), while not the first survival horror game, planted the seeds of what would become known as the survival horror genre today. It established the formula that would later flourish on CD-ROM based consoles, with games such as Resident Evil and Silent Hill.

Adventure games continued to evolve, with Sierra Entertainment’s King's Quest series, and LucasFilms'/LucasArts' Monkey Island series bringing graphical interaction and the creation of the concept of "point-and-click" gaming. Myst and its sequels inspired a new style of puzzle-based adventure games. Published in 1993, Myst itself was one of the first computer games to make full use of the new high-capacity CD-ROM storage format. Despite Myst’s mainstream success, the increased popularity of action-based and real-time games led adventure games and simulation video games, both mainstays of computer games in earlier decades, to begin to fade into obscurity.

It was in the 1990s that Maxis began publishing its successful line of "Sim" games, beginning with SimCity, and continuing with a variety of titles, such as SimEarth, SimCity 2000, SimAnt, SimTower, and the best-selling PC game in history, The Sims, in early 2000.

In 1996, 3dfx Interactive released the Voodoo chipset, leading to the first affordable 3D accelerator cards for personal computers. These devoted 3D rendering daughter cards performed a portion of the computations required for more-detailed three-dimensional graphics (mainly texture filtering), allowing for more-detailed graphics than would be possible if the CPU were required to handle both game logic and all the graphical tasks. First-person shooter games (notably Quake) were among the first to take advantage of this new technology. While other games would also make use of it, the FPS would become the chief driving force behind the development of new 3D hardware, as well as the yardstick by which its performance would be measured, usually quantified as the number of frames per second rendered for a particular scene in a particular game.

Several other, less-mainstream, genres were created in this decade. Looking Glass Studios' Thief: The Dark Project and its sequel were the first to coin the term "first person sneaker", although it is questionable whether they are the first "first person stealth" games. Turn-based strategy progressed further, with the Heroes of Might and Magic (HOMM) series (from The 3DO Company) luring many mainstream gamers into this complex genre.

The first true MUDs (Multi-User Dungeons) were developed in the early 90s. Id Software’s 1996 game Quake pioneered play over the Internet in first-person shooters. Internet multiplayer capability became a de facto requirement in almost all FPS games. Other genres also began to offer online play, including RTS games like Microsoft Game Studios’ Age of Empires, Blizzard’s Warcraft and StarCraft series, and turn-based games such as Heroes of Might and Magic. MMORPGs (Massively multiplayer online role-playing game), such as Ultima Online and EverQuest freed users from the limited number of simultaneous players in other games and brought the MUD concept of persistent worlds to graphical multiplayer games. Developments in web browser plug-ins like Java and Adobe Flash allowed for simple browser-based games. These are small single player or multiplayer games that can be quickly downloaded and played from within a web browser without installation. Their most popular use is for puzzle games, side-scrollers, classic arcade games, and multiplayer card and board games.

Few new genres have been created since the advent of the FPS and RTS, with the possible exception of the third-person shooter. Games such as Grand Theft Auto III, Tom Clancy's Splinter Cell, Enter the Matrix, and Hitman all use a third-person camera perspective, but are otherwise very similar to their first-person counterparts.

Decline of arcades
With the advent of 16-bit and 32-bit consoles, home video games began to approach the level of graphics seen in arcade games. An increasing number of players would wait for popular arcade games to be ported to consoles rather than going out. Arcades experienced a resurgence in the early to mid 1990s with games such as Street Fighter II and Mortal Kombat and other games in the one-on-one fighting game genre, and NBA Jam. As patronage of arcades declined, many were forced to close down. Classic coin-operated games have largely become the province of dedicated hobbyists and as a tertiary attraction for some businesses, such as movie theaters, batting cages, miniature golf, and arcades attached to game stores such as F.Y.E..

The gap left by the old corner arcades was partly filled by large amusement centers dedicated to providing clean, safe environments and expensive game control systems not available to home users. These are usually based on sports like skiing or cycling, as well as rhythm games like Dance Dance Revolution, which have carved out a large slice of the market. Dave & Buster's and GameWorks are two large chains in the United States with this type of environment. Aimed at adults, they feature full service restaurants with full liquor bars and have a wide variety of video game and hands on electronic gaming options. Chuck E. Cheese's is a similar type of establishment focused towards children.

Handhelds come of age
In 1989, Nintendo released the Game Boy, the first handheld console since the ill-fated Microvision ten years before. The design team headed by Gunpei Yokoi had also been responsible for the Game & Watch systems. Included with the system was Tetris, a popular puzzle game. Several rival handhelds also made their debut around that time, including the Sega Game Gear and Atari Lynx (the first handheld with color LCD display). Although most other systems were more technologically advanced, they were hampered by higher battery consumption and less third-party developer support. While some of the other systems remained in production until the mid-90s, the Game Boy remained at the top spot in sales throughout its lifespan.

Mobile phone gaming
Mobile phones became videogaming platforms when Nokia installed Snake onto its line of mobile phones in 1998. Soon every major phone brand offered "time killer games" that could be played in very short moments such as waiting for a bus. Mobile phone games early on were limited by the modest size of the phone screens that were all monochrome and the very limited amount of memory and processing power on phones, as well as the drain on the battery.

" FOURTH GENERATION (1989–1997) "
The Sega Mega Drive (known in North America as the Sega Genesis) proved its worth early on after its debut in 1989. Nintendo responded with its own next generation system known as the Super NES in 1991. The TurboGrafx-16 debuted early on alongside the Genesis, but did not achieve a large following in the U.S. due to a limited library of games and excessive distribution restrictions imposed by Hudson.

The intense competition of this time was also a period of not entirely truthful marketing. The TurboGrafx-16 was billed as the first 16-bit system but its central processor was an 8-bit HuC6280, with only its HuC6260 graphics processor being a true 16-bit chip. Additionally, the much earlier Mattel Intellivision contained a 16-bit processor. Sega, too, was known to stretch the truth in its marketing approach; they used the term "Blast Processing" to describe the simple fact that their console's CPU ran at a higher clock speed than that of the SNES (7.67 MHz vs 3.58 MHz).

In Japan, the 1987 success of the PC Engine (as the TurboGrafx-16 was known there) against the Famicom and CD drive peripheral allowed it to fend off the Mega Drive (Genesis) in 1988, which never really caught on to the same degree as outside Japan. The PC Engine eventually lost out to the Super Famicom, but, due to its popular CD add-ons, retained enough of a user base to support new games well into the late 1990s.

CD-ROM drives were first seen in this generation, as add-ons for the PC Engine in 1988 and the Mega Drive in 1991. Basic 3D graphics entered the mainstream with flat-shaded polygons enabled by additional processors in game cartridges like Virtua Racing and Star Fox.

SNK's Neo-Geo was the most expensive console by a wide margin when it was released in 1990, and would remain so for years. It was also capable of 2D graphics in a quality level years ahead of other consoles. The reason for this was that it contained the same hardware that was found in SNK's arcade games. This was the first time since the home Pong machines that a true-to-the-arcade experience could be had at home.

" FIFTH GENERATION (1994–2002) "

In 1993, Atari re-entered the home console market with the introduction of the Atari Jaguar. Also in 1993, The 3DO Company released the 3DO Interactive Multiplayer, which, though highly advertised and promoted, failed to catch up to the sales of the Jaguar, due its high pricetag. Both consoles had very low sales and few quality games, eventually leading to their demise. In 1994, three new consoles were released in Japan: the Sega Saturn, the PlayStation, and the PC-FX, the Saturn and the PlayStation later seeing release in North America in 1995. The PlayStation quickly outsold all of its competitors, with the exception of the aging Super Nintendo Entertainment System, which still had the support of many major game companies.

After many delays, Nintendo released its 64-bit console, the Nintendo 64 in 1996. The flagship title, Super Mario 64, became a defining title for 3D platformer games.

PaRappa the Rapper popularized rhythm, or music video games in Japan with its 1996 debut on the PlayStation. Subsequent music and dance games like beatmania and Dance Dance Revolution became ubiquitous attractions in Japanese arcades. While Parappa, DDR, and other games found a cult following when brought to North America, music games would not gain a wide audience in the market until the next decade.

Other milestone games of the era include Rare's Nintendo 64 title GoldenEye 007 (1997), which was critically acclaimed for bringing innovation as being the first major first-person shooter that was exclusive to a console, and for pioneering certain features that became staples of the genre, such as scopes, headshots, and objective-based missions.[citation needed] The Legend of Zelda: Ocarina of Time (1998), Nintendo's 3D debut for the The Legend of Zelda adventure game series featured innovations such as Z-targeting, used in later games of similar genres.

Nintendo's choice to use cartridges instead of CD-ROMs for the Nintendo 64, unique among the consoles of this period, proved to have negative consequences. While cartridges were faster and combated piracy, CDs could hold far more data and were much cheaper to produce, causing many game companies to turn to Nintendo's CD-based competitors. In particular, SquareSoft, which had released all previous games in its Final Fantasy series for Nintendo consoles, now turned to the PlayStation; Final Fantasy VII (1997) was a huge success, establishing the popularity of role-playing games in the west and making the PlayStation the primary console for the genre.

By the end of this period, Sony had become the leader in the video game market. The Saturn was moderately successful in Japan but a failure in North America and Europe, leaving Sega outside of the main competition. The N64 achieved huge success in North America and Europe, though it never surpassed PlayStation's sales. The N64 was also successful in Japan, even though it failed to repeat the tremendous success of the Famicom and Super Famicom there due to stiff competition by PlayStation.

" SIXTH GENERATION (1998–2008) "
In the sixth generation of video game consoles, Sega exited the hardware market, Nintendo fell behind, Sony solidified its lead in the industry, and Microsoft developed a gaming console.

The Dreamcast, introduced in 1998, opened the generation but failed to become a hit, and faded from the market before the subsequent consoles appeared. Sega retreated to the third-party game market. Sony opened the new decade with the PlayStation 2, which would go on to become the top-selling sixth generation console. Nintendo followed a year later with the GameCube, their first disc-based console. Though more or less equal with Sony's system in technical specifications, the GameCube suffered from a lack of third-party games compared to Sony's system, and was hindered by a reputation for being a "kid's console" and lacking the mature games the current market appeared to want.

Before the end of 2001, Microsoft Corporation, best known for its Windows operating system and its professional productivity software, judged the console market profitable for entry with the decline of Sega and Nintendo, and introduced the Xbox. Based on Intel's Pentium III CPU, the console used much PC technology to leverage its internal development. In order to maintain its hold in the market, Microsoft reportedly sold the Xbox at a significant loss[11]and concentrated on drawing profit from game development and publishing. Shortly after its release in November 2001 Bungie Studio's Halo: Combat Evolved instantly became the driving point of the Xbox's success, and the Halo Series would later go on to become one of the most successful console shooters of all time. By the end of the generation, the Xbox had drawn even with the GameCube in sales globally, but since nearly all of its sales were in North America, it pushed Nintendo into third place in the American market.

Nintendo still dominated the handheld gaming market in this generation. The Game Boy Color, in 1998, and then the Game Boy Advance in 2001, maintained Nintendo's market position. Finnish cellphone maker Nokia entered the handheld scene with the N-Gage, but it failed to win a significant following.

Online gaming rises to prominence
As affordable broadband Internet connectivity spread, many publishers turned to online gaming as a way of innovating. Massively multiplayer online role-playing game (MMORPGs) featured significant titles for the PC market like World of Warcraft and Ultima Online. Historically, console based MMORPGs have been few in number due to the lack of bundled Internet connectivity options for the platforms. This made it hard to establish a large enough subscription community to justify the development costs. The first significant console MMORPGs were Phantasy Star Online on the Sega Dreamcast (which had a built in modem and after market Ethernet adapter), followed by Final Fantasy XI for the Sony PlayStation 2 (an aftermarket Ethernet adapter was shipped to support this game). Every major platform released since the Dreamcast has ether been bundled with the ability to support an Internet connection or has had the option available as an aftermarket add-on.

Rise of casual PC games
Beginning with PCs, a new trend in casual gaming, games with limited complexity that were designed for shortened or impromptu play sessions, began to draw attention from the industry. Many were puzzle games, such as Popcap's Bejeweled and Diner Dash, while others were games with a more relaxed pace and open-ended play. The biggest hit was The Sims by Maxis, which went on to become the best selling computer game of all time, surpassing Myst.

Console gaming largely continued the trend established by the PlayStation toward increasingly complex, sophisticated, and adult-oriented gameplay. Most of the successful sixth-generation console games were games rated T and M by the ESRB, including many now-classic gaming franchises such as Halo, Resident Evil, and Grand Theft Auto, the latter of which was notable for both its success and its notoriety. Even Nintendo, widely known for its aversion to adult content (with very few exceptions most notably Conker's Bad Fur Day for the Nintendo 64), published its first M-rated game, Silicon Knights's Eternal Darkness: Sanity's Requiem, and the GameCube was the temporary exclusive platform for Capcom's Resident Evil 4. This trend in hardcore console gaming would partially be reversed with the 7th generation release of the Wii.

" SEVENTH GENERATION ( 2004 TO PRESENT) "
A major rift opened in console gaming philosophy and design in the seventh generation, with some calling the identification of video game "generations" questionable and arbitrary, while PC gaming began to go into relative decline as major publishers steered their efforts to consoles.

The generation opened early for handheld consoles, as Nintendo introduced their Nintendo DS and Sony premiered the PlayStation Portable (PSP) within a month of each other in 2004. While the PSP boasted superior graphics and power, following a trend established since the mid 1980s, Nintendo gambled on a lower-power design but featuring a novel control interface. The DS's two screens, one of which was touch-sensitive, proved extremely popular with consumers, especially young kids and middle-aged gamers, who were drawn to the device by Nintendo's Nintendogs and Brain Age series, respectively. While the PSP attracted a significant portion of veteran gamers, the DS allowed Nintendo to continue its dominance in handheld gaming. Nintendo updated their line with the Nintendo DS Lite in 2006, and the Nintendo DSi in 2008 (Japan) and 2009 (Americas and Europe), while Sony updated the PSP in 2007. Nokia withdrew their N-Gage platform in 2004 but reintroduced it in late 2008. Now with the release of the Apple Inc. iPhone and iPod Touch, 3D gaming is more portable than ever and offers a range of new sensors, including but not limited to, the accelerometer.

In console gaming, Microsoft stepped forward first in November 2005 with the Xbox 360, and Sony followed in 2006 with the PlayStation 3, released in Europe in March 2007. Setting the technology standard for the generation, both featured high-definition graphics, large hard disk-based secondary storage, integrated networking, and a companion on-line gameplay and sales platform, with Xbox Live and the PlayStation Network, respectively. Both were formidable systems that were the first to challenge personal computers in power while offering a relatively modest price compared to them. While both were more expensive than most past consoles, the Xbox 360 enjoyed a substantial price edge, selling for either $300 or $400 depending on model, while the PS3 launched with models priced at $500 and $600. The top-of-the-line PS3 was the most expensive game console on the market since Panasonic's version of the 3DO, which was around $700.

Nintendo was not expected to compete credibly at all, with most industry analysts predicting a distant third place finish for its new Revolution console, later renamed Wii, introduced a couple days after the PS3, and one even going so far as to predict a market exit similar to Sega. Instead, Nintendo pulled off an industry turnaround in business. While the Wii's power was greater than that of last generation's consoles, it was clearly behind Microsoft and Sonys' consoles, and Nintendo themselves refused to publish or confirm technical specifications, instead touting the console's new control scheme, featuring motion-based control and infrared-based pointing. Many gamers, publishers, and analysts dismissed the Wii as an underpowered curiosity, but were surprised as the console sold out through the 2006 Christmas season, and remained so through the next 18 months, becoming the fastest selling game console in most of the world's gaming markets.

Increases in development budgets
With high definition video an undeniable hit with veteran gamers seeking immersive experiences, expectations for visuals in games along with the increasing complexity of productions resulted in a spike in the development budgets of gaming companies. While many game studios saw their Xbox 360 projects pay off, the unexpected weakness of PS3 sales resulted in heavy losses for some developers, and many publishers broke previously arranged PS3 exclusivity arrangements or cancelled PS3 game projects entirely in order to cut losses.

Nintendo capitalizes on casual gaming
Meanwhile, Nintendo took cues from PC gaming and their own success with the Nintendo Wii, and crafted games that capitalized on the intuitive nature of motion control. Emphasis on gameplay turned comparatively simple games into unlikely runaway hits, including the bundled game, Wii Sports, and Wii Fit. As the Wii sales spiked, many publishers were caught unprepared and responded by assembling hastily-created titles to fill the void. Although some hardcore games continued to be produced by Nintendo, many of their classic franchises were reworked into "bridge games", meant to provide new gamers crossover experiences from casual gaming to deeper experiences, including their flagship Wii title, Super Mario Galaxy, which in spite of its standard-resolution graphics dominated critics' "best-of" lists for 2007. Many others, however, strongly criticized Nintendo for its apparent spurning of its core gamer base in favor of a demographic many warned would be fickle and difficult to keep engaged.

Motion controls revolutionize game control
The way gamers interact with games changed dramatically, especially with Nintendo's wholesale embrace of motion control as a standard method of interaction. The Wii Remote implemented the principles well enough to be a worldwide success, but Sony also experimented with motion in its Sixaxis and subsequently DualShock3 controller for the PS3, and Microsoft continually mentions interest in developing the technology for the Xbox 360. While the Wii's infrared-based pointing system has been praised widely, and cited as a primary reason for the success of games such as Nintendo's Metroid Prime 3: Corruption and EA's Medal of Honor: Heroes 2, reliable motion controls have been more elusive. Even the most refined motion controls fail to achieve 1-to-1 reproduction of player motion on-screen. Nintendo's 2008 announcement of its MotionPlus module was intended to address critics' concerns.

Alternate controllers are also continuing to be important in gaming, as the increasingly involved controllers associated with Red Octane's Guitar Hero series and Harmonix's Rock Band demonstrate. Nintendo has produced a some add-on attachments meant to adapt the Wii Remote to specific games, such as the Wii Zapper for shooting games and the Wii Wheel for driving games. They also extended control capabilities to players' feet with the introduction of the Balance Board with Wii Fit, with third party titles from THQ, EA, and others that will integrate foot control coming in late 2008 and early 2009.

13) HISTORY OF THE "WORLD WIDE WEB"

2009-06-19T15:01:00.000-07:00

The World Wide Web ("WWW" or simply the "Web") is a global information medium which users can read and write via computers connected to the Internet. The term is often mistakenly used as a synonym for the Internet itself, but the Web is a service that operates over the Internet, as e-mail does. The history of the Internet dates back significantly further than that of the World Wide Web.

The hypertext portion of the Web in particular has an intricate intellectual history; notable influences and precursors include Vannevar Bush's Memex, IBM's Generalized Markup Language, and Ted Nelson's Project Xanadu.

Today, the Web and the Internet allow connectivity from literally everywhere on earth—even ships at sea and in outer space

The concept of a home-based global information system goes at least as far back as "A Logic Named Joe", a 1946 short story by Murray Leinster, in which computer terminals, called "logics," were in every home. Although the computer system in the story is centralized, the story captures some of the feeling of the ubiquitous information explosion driven by the Web.

1980-91: Development of the World Wide Web

In 1980, the Englishman Tim Berners-Lee, an independent contractor at the EuropeanOrganization for Nuclear Research (CERN), Switzerland, built ENQUIRE, as a personal database of people and software models, but also as a way to play with hypertext; each new page of information in ENQUIRE had to be linked to an existing page.

In 1984 Berners-Lee returned to CERN, and considered its problems of information presentation: physicists from around the world needed to share data, with no common machines and no common presentation software. He wrote a proposal in March 1989 for "a large hypertext database with typed links", but it generated little interest. His boss, Mike Sendall, encouraged Berners-Lee to begin implementing his system on a newly acquired NeXT workstation. He considered several names, including Information Mesh, The Information Mine (turned down as it abbreviates to TIM, the WWW's creator's name) or Mine of Information (turned down because it abbreviates to MOI which is "Me" in French), but settled on World Wide Web.

He found an enthusiastic collaborator in Robert Cailliau, who rewrote the proposal (published on November 12, 1990) and sought resources within CERN. Berners-Lee and Cailliau pitched their ideas to the European Conference on Hypertext Technology in September 1990, but found no vendors who could appreciate their vision of marrying hypertext with the Internet.

By Christmas 1990, Berners-Lee had built all the tools necessary for a working Web: the HyperText Transfer Protocol (HTTP) 0.9, the HyperText Markup Language (HTML), the first Web browser (named WorldWideWeb, which was also a Web editor), the first HTTP server software (later known as CERN httpd), the first web server (http://info.cern.ch), and the first Web pages that described the project itself. The browser could access Usenet newsgroups and FTP files as well. However, it could run only on the NeXT; Nicola Pellow therefore created a simple text browser that could run on almost any computer. To encourage use within CERN, they put the CERN telephone directory on the web — previously users had had to log onto the mainframe in order to look up phone numbers.

Paul Kunz from the Stanford Linear Accelerator Center visited CERN in May 1991, and was captivated by the Web. He brought the NeXT software back to SLAC, where librarian Louise Addis adapted it for the VM/CMS operating system on the IBM mainframe as a way to display SLAC’s catalog of online documents; this was the first web server outside of Europe and the first in North America.

On August 6, 1991, Berners-Lee posted a short summary of the World Wide Web project on the alt.hypertext newsgroup. This date also marked the debut of the Web as a publicly available service on the Internet.

The WorldWideWeb (WWW) project aims to allow all links to be made to any information anywhere. The WWW project was started to allow high energy physicists to share data, news, and documentation. We are very interested in spreading the web to other areas, and having gateway servers for other data. Collaborators welcome!" —from Tim Berners-Lee's first message

An early CERN-related contribution to the Web was the parody band Les Horribles Cernettes, whose promotional image is believed to be among the Web's first five pictures.

1992-1995: Growth of the WWW
In keeping with its birth at CERN, early adopters of the World Wide Web were primarily university-based scientific departments or physics laboratories such as Fermilab and SLAC.

Early websites intermingled links for both the HTTP web protocol and the then-popular Gopher protocol, which provided access to content through hypertext menus presented as a file system rather than through HTML files. Early Web users would navigate either by bookmarking popular directory pages, such as Berners-Lee's first site at http://info.cern.ch/, or by consulting updated lists such as the NCSA "What's New" page. Some sites were also indexed by WAIS, enabling users to submit full-text searches similar to the capability later provided by search engines.

There was still no graphical browser available for computers besides the NeXT. This gap was filled in April 1992 with the release of Erwise, an application developed at Helsinki University of Technology, and in May by ViolaWWW, created by Pei-Yuan Wei, which included advanced features such as embedded graphics, scripting, and animation. Both programs ran on the X Window System for Unix.

Students at the University of Kansas adapted an existing text-only hypertext browser, Lynx, to access the web. Lynx was available on Unix and DOS, and some web designers, unimpressed with glossy graphical websites, held that a website not accessible through Lynx wasn’t worth visiting.

Early Browsers
The turning point for the World Wide Web was the introduction of the Mosaic web browser in 1993, a graphical browser developed by a team at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign (UIUC), led by Marc Andreessen. Funding for Mosaic came from the High-Performance Computing and Communications Initiative, a funding program initiated by then-Senator Al Gore's High Performance Computing and Communication Act of 1991 also known as the Gore Bill.

The origins of Mosaic had begun in 1992. In November 1992, the NCSA at the University of Illinois (UIUC) established a website. In December 1992, Andreessen and Eric Bina, students attending UIUC and working at the NCSA, began work on Mosaic. They released an X Window browser in February 1993. It gained popularity due to its strong support of integrated multimedia, and the authors’ rapid response to user bug reports and recommendations for new features.

The first Microsoft Windows browser was Cello, written by Thomas R. Bruce for the Legal Information Institute at Cornell Law School to provide legal information, since more lawyers had access to Windows than to Unix. Cello was released in June 1993.

After graduation from UIUC, Andreessen and James H. Clark, former CEO of Silicon Graphics, met and formed Mosaic Communications Corporation to develop the Mosaic browser commercially. The company changed its name to Netscape in April 1994, and the browser was developed further as Netscape Navigator.

Web organization
In May 1994 the first International WWW Conference, organized by Robert Cailliau, was held at CERN; the conference has been held every year since. In April 1993 CERN had agreed that anyone could use the Web protocol and code royalty-free; this was in part a reaction to the perturbation caused by the University of Minnesota announcing that it would begin charging license fees for its implementation of the Gopher protocol.

In September 1994, Berners-Lee founded the World Wide Web Consortium (W3C) at the Massachusetts Institute of Technology with support from the Defense Advanced Research Projects Agency (DARPA) and the European Commission. It comprised various companies that were willing to create standards and recommendations to improve the quality of the Web. Berners-Lee made the Web available freely, with no patent and no royalties due. The World Wide Web Consortium decided that their standards must be based on royalty-free technology, so they can be easily adopted by anyone.

1996-1998: Commercialization of the WWW
By 1996 it became obvious to most publicly traded companies that a public Web presence was no longer optional. Though at first people saw mainly the possibilities of free publishing and instant worldwide information, increasing familiarity with two-way communication over the "Web" led to the possibility of direct Web-based commerce (e-commerce) and instantaneous group communications worldwide. More dotcoms, displaying products on hypertext webpages, were added into the Web.

1999-2001: "Dot-com" boom and bust
The low interest rates in 1998–99 helped increase the start-up capital amounts. Although a number of these new entrepreneurs had realistic plans and administrative ability, most of them lacked these characteristics but were able to sell their ideas to investors because of the novelty of the dot-com concept.

Historically, the dot-com boom can be seen as similar to a number of other technology-inspired booms of the past including railroads in the 1840s, radio in the 1920s, transistor electronics in the 1950s, computer time-sharing in the 1960s, and home computers and biotechnology in the early 1980s.

In 2001 the bubble burst, and many dot-com startups went out of business after burning through their venture capital and failing to become profitable.

2002-Present: The Web becomes ubiquitous
In the aftermath of the dot-com bubble, telecommunications companies had a great deal of overcapacity as many Internet business clients went bust. That, plus ongoing investment in local cell infrastructure kept connectivity charges low, and helping to make high-speed Internet connectivity more affordable. During this time, a handful of companies found success developing business models that helped make the World Wide Web a more compelling experience. These include airline booking sites, Google's search engine and its profitable approach to simplified, keyword-based advertising, as well as Ebay's do-it-yourself auction site and Amazon.com's big selection of books.

This new era also begot social networking websites, such as MySpace, Xanga, Friendster, and Facebook, which, though unpopular at first, very rapidly gained acceptance in becoming a major part of youth culture.

Web 2.0
Beginning in 2002, new ideas for sharing and exchanging content ad hoc, such as Weblogs and RSS, rapidly gained acceptance on the Web. This new model for information exchange, primarily featuring DIY user-edited and generated websites, was coined Web 2.0.

The Web 2.0 boom saw many new service-oriented startups catering to a new, democratized Web. Some believe it will be followed by the full realization of a Semantic Web.

Tim Berners-Lee originally expressed the vision of the Semantic Web as follows:

""I have a dream for the Web [in which computers] become capable of analyzing all the data on the Web – the content, links, and transactions between people and computers. A ‘Semantic Web’, which should make this possible, has yet to emerge, but when it does, the day-to-day mechanisms of trade, bureaucracy and our daily lives will be handled by machines talking to machines. The ‘intelligent agents’ people have touted for ages will finally materialize.""

Tim Berners-Lee, 1999

Predictably, as the World Wide Web became easier to query, attained a higher degree of usability, and shed its esoteric reputation, it gained a sense of organization and unsophistication which opened the floodgates and ushered in a rapid period of popularization. New sites such as Wikipedia and its sister projects proved revolutionary in executing the User edited content concept. In 2005, 3 ex-PayPal employees formed a video viewing website called YouTube. Only a year later, YouTube was proven the most quickly popularized website in history, and even started a new concept of user-submitted content in major events, as in the CNN-YouTube Presidential Debates.

Continued extension of the World Wide Web has focused on connecting devices to the Internet, coined Intelligent Device Management. As Internet connectivity becomes ubiquitous, manufacturers have started to leverage the expanded computing power of their devices to enhance their usability and capability. Through Internet connectivity, manufacturers are now able to interact with the devices they have sold and shipped to their customers, and customers are able to interact with the manufacturer (and other providers) to access new content.

12)HISTORY OF THE INTERNET

2009-06-19T14:54:00.000-07:00

Before the widespread internetworking that led to the Internet, most communication networks were limited by their nature to only allow communications between the stations on the network, and the prevalent computer networking method was based on the central mainframe computer model. Several research programs began to explore and articulate principles of networking between separate physical networks, leading to the development of the packet switching model of digital networking. These research efforts included those of the laboratories of Donald Davies (NPL), Paul Baran (RAND Corporation), and Leonard Kleinrock's MIT and UCLA.The research led to the development of several packet-switched networking solutions in the late 1960s and 1970s, including ARPANET and the X.25 protocols. Additionally, public access and hobbyist networking systems grew in popularity, including unix-to-unix copy (UUCP) and FidoNet. They were however still disjointed separate networks, served only by limited gateways between networks. This led to the application of packet switching to develop a protocol for inter-networking, where multiple different networks could be joined together into a super-framework of networks. By defining a simple common network system, the Internet protocol suite, the concept of the network could be separated from its physical implementation. This spread of inter-network began to form into the idea of a global inter-network that would be called 'The Internet', and this began to quickly spread as existing networks were converted to become compatible with this. This spread quickly across the advanced telecommunication networks of the western world, and then began to penetrate into the rest of the world as it became the de-facto international standard and global network. However, the disparity of growth led to a digital divide that is still a concern today.

Following commercialisation and introduction of privately run Internet Service Providers in the 1980s, and its expansion into popular use in the 1990s, the Internet has had a drastic impact on culture and commerce. This includes the rise of near instant communication by e-mail, text based discussion forums, and the World Wide Web. Investor speculation in new markets provided by these innovations would also lead to the inflation and collapse of the Dot-com bubble, a major market collapse. But despite this, the Internet continues to grow.

Before the Internet
In the 1950s and early 1960s, prior to the widespread inter-networking that led to the Internet, most communication networks were limited in that they only allowed communications between the stations on the network. Some networks had gateways or bridges between them, but these bridges were often limited or built specifically for a single use. One prevalent computer networking method was based on the central mainframe method, simply allowing its terminals to be connected via long leased lines. This method was used in the 1950s by Project RAND to support researchers such as Herbert Simon, in Pittsburgh, Pennsylvania, when collaborating across the continent with researchers in Sullivan, Illinois, on automated theorem proving and artificial intelligence.The research led to the development of several packet-switched networking solutions in the late 1960s and 1970s, including ARPANET and the X.25 protocols. Additionally, public access and hobbyist networking systems grew in popularity, including unix-to-unix copy (UUCP) and FidoNet. They were however still disjointed separate networks, served only by limited gateways between networks. This led to the application of packet switching to develop a protocol for inter-networking, where multiple different networks could be joined together into a super-framework of networks. By defining a simple common network system, the Internet protocol suite, the concept of the network could be separated from its physical implementation. This spread of inter-network began to form into the idea of a global inter-network that would be called 'The Internet', and this began to quickly spread as existing networks were converted to become compatible with this. This spread quickly across the advanced telecommunication networks of the western world, and then began to penetrate into the rest of the world as it became the de-facto international standard and global network. However, the disparity of growth led to a digital divide that is still a concern today.

Three terminals and an ARPA

A fundamental pioneer in the call for a global network, J.C.R. Licklider, articulated the ideas in his January 1960 paper, Man-Computer Symbiosis.

"A network of such [computers], connected to one another by wide-band communication lines [which provided] the functions of present-day libraries together with anticipated advances in information storage and retrieval and [other] symbiotic functions."

In October 1962, Licklider was appointed head of the United States Department of Defense's Advanced Research Projects Agency, now known as DARPA, within the information processing office. There he formed an informal group within DARPA to further computer research. As part of the information processing office's role, three network terminals had been installed: one for System Development Corporation in Santa Monica, one for Project Genie at the University of California, Berkeley and one for the Compatible Time-Sharing System project at the Massachusetts Institute of Technology (MIT). Licklider's identified need for inter-networking would be made obvious by the apparent waste of resources this caused.

"For each of these three terminals, I had three different sets of user commands. So if I was talking online with someone at S.D.C. and I wanted to talk to someone I knew at Berkeley or M.I.T. about this, I had to get up from the S.D.C. terminal, go over and log into the other terminal and get in touch with them. [...] I said, it's obvious what to do (But I don't want to do it): If you have these three terminals, there ought to be one terminal that goes anywhere you want to go where you have interactive computing. That idea is the ARPAnet."

Packet switching

At the tip of the inter-networking problem lay the issue of connecting separate physical networks to form one logical network, with much wasted capacity inside the assorted separate networks. During the 1960s, Donald Davies (NPL), Paul Baran (RAND Corporation), and Leonard Kleinrock (MIT) developed and implemented packet switching. Early networks used for the command and control of nuclear forces were message switched, not packet-switched, although current strategic military networks are, indeed, packet-switching and connectionless. Baran's research had approached packet switching from studies of decentralisation to avoid combat damage compromising the entire network.

Networks that led to the Internet

Promoted to the head of the information processing office at DARPA, Robert Taylor intended to realize Licklider's ideas of an interconnected networking system. Bringing in Larry Roberts from MIT, he initiated a project to build such a network. The first ARPANET link was established between the University of California, Los Angeles and the Stanford Research Institute on 22:30 hours on October 29, 1969. By December 5, 1969, a 4-node network was connected by adding the University of Utah and the University of California, Santa Barbara. Building on ideas developed in ALOHAnet, the ARPANET grew rapidly. By 1981, the number of hosts had grown to 213, with a new host being added approximately every twenty days.

ARPANET became the technical core of what would become the Internet, and a primary tool in developing the technologies used. ARPANET development was centered around the Request for Comments (RFC) process, still used today for proposing and distributing Internet Protocols and Systems. RFC 1, entitled "Host Software", was written by Steve Crocker from the University of California, Los Angeles, and published on April 7, 1969. These early years were documented in the 1972 film Computer Networks: The Heralds of Resource Sharing.

International collaborations on ARPANET were sparse. For various political reasons, European developers were concerned with developing the X.25 networks. Notable exceptions were the Norwegian Seismic Array (NORSAR) in 1972, followed in 1973 by Sweden with satellite links to the Tanum Earth Station and University College London.

" 2) X.25 and public access "

Following on from ARPA's research, packet switching network standards were developed by the International Telecommunication Union (ITU) in the form of X.25 and related standards. In 1974, X.25 formed the basis for the SERCnet network between British academic and research sites, which later became JANET. The initial ITU Standard on X.25 was approved in March 1976. This standard was based on the concept of virtual circuits.

The British Post Office, Western Union International and Tymnet collaborated to create the first international packet switched network, referred to as the International Packet Switched Service (IPSS), in 1978. This network grew from Europe and the US to cover Canada, Hong Kong and Australia by 1981. By the 1990s it provided a worldwide networking infrastructure.

Unlike ARPAnet, X.25 was also commonly available for business use. Telenet offered its Telemail electronic mail service, but this was oriented to enterprise use rather than the general email of ARPANET.

The first dial-in public networks used asynchronous TTY terminal protocols to reach a concentrator operated by the public network. Some public networks, such as CompuServe used X.25 to multiplex the terminal sessions into their packet-switched backbones, while others, such as Tymnet, used proprietary protocols. In 1979, CompuServe became the first service to offer electronic mail capabilities and technical support to personal computer users. The company broke new ground again in 1980 as the first to offer real-time chat with its CB Simulator. There were also the America Online (AOL) and Prodigy dial in networks and many bulletin board system (BBS) networks such as FidoNet. FidoNet in particular was popular amongst hobbyist computer users, many of them hackers and amateur radio operators.

" 3) UUCP "

In 1979, two students at Duke University, Tom Truscott and Jim Ellis, came up with the idea of using simple Bourne shell scripts to transfer news and messages on a serial line with nearby University of North Carolina at Chapel Hill. Following public release of the software, the mesh of UUCP hosts forwarding on the Usenet news rapidly expanded. UUCPnet, as it would later be named, also created gateways and links between FidoNet and dial-up BBS hosts. UUCP networks spread quickly due to the lower costs involved, and ability to use existing leased lines, X.25 links or even ARPANET connections. By 1981 the number of UUCP hosts had grown to 550, nearly doubling to 940 in 1984. - Sublink Network, operating since 1987 and officialy founded in Italy in 1989, based its interconnectivity upon UUCP to redistribute mail and news groups messages throughout its Italian nodes (about 100 at the time) owned both by private individuals and small companies. Sublink Network represented possibly one of the first examples of the internet technology becoming progress through popular diffusion.

Merging the networks and creating the Internet

" TCP/IP "

With so many different network methods, something was needed to unify them. Robert E. Kahn of DARPA and ARPANET recruited Vinton Cerf of Stanford University to work with him on the problem. By 1973, they had soon worked out a fundamental reformulation, where the differences between network protocols were hidden by using a common internetwork protocol, and instead of the network being responsible for reliability, as in the ARPANET, the hosts became responsible. Cerf credits Hubert Zimmerman, Gerard LeLann and Louis Pouzin (designer of the CYCLADES network) with important work on this design.

Map of the TCP/IP test network in January 1982

The specification of the resulting protocol, RFC 675 - Specification of Internet Transmission Control Program, by Vinton Cerf, Yogen Dalal and Carl Sunshine, Network Working Group, December, 1974, contains the first attested use of the term internet, as a shorthand for internetworking; later RFCs repeat this use, so the word started out as an adjective rather than the noun it is today.

With the role of the network reduced to the bare minimum, it became possible to join almost any networks together, no matter what their characteristics were, thereby solving Kahn's initial problem. DARPA agreed to fund development of prototype software, and after several years of work, the first somewhat crude demonstration of a gateway between the Packet Radio network in the SF Bay area and the ARPANET was conducted. On November 22, 1977 a three network demonstration was conducted including the ARPANET, the Packet Radio Network and the Atlantic Packet Satellite network—all sponsored by DARPA. Stemming from the first specifications of TCP in 1974, TCP/IP emerged in mid-late 1978 in nearly final form. By 1981, the associated standards were published as RFCs 791, 792 and 793 and adopted for use. DARPA sponsored or encouraged the development of TCP/IP implementations for many operating systems and then scheduled a migration of all hosts on all of its packet networks to TCP/IP. On January 1, 1983, TCP/IP protocols became the only approved protocol on the ARPANET, replacing the earlier NCP protocol.

ARPANET to Several Federal Wide Area Networks: MILNET, NSI, and
NSFNet

After the ARPANET had been up and running for several years, ARPA looked for another agency to hand off the network to; ARPA's primary mission was funding cutting edge research and development, not running a communications utility. Eventually, in July 1975, the network had been turned over to the Defense Communications Agency, also part of the Department of Defense. In 1983, the U.S. military portion of the ARPANET was broken off as a separate network, the MILNET. MILNET subsequently became the unclassified but military-only NIPRNET, in parallel with the SECRET-level SIPRNET and JWICS for TOP SECRET and above. NIPRNET does have controlled security gateways to the public Internet.

Commemorative plaque listing some of the early Internet pioneers

The networks based around the ARPANET were government funded and therefore restricted to noncommercial uses such as research; unrelated commercial use was strictly forbidden. This initially restricted connections to military sites and universities. During the 1980s, the connections expanded to more educational institutions, and even to a growing number of companies such as Digital Equipment Corporation and Hewlett-Packard, which were participating in research projects or providing services to those who were.

Several other branches of the U.S. government, the National Aeronautics and Space Agency (NASA), the National Science Foundation (NSF), and the Department of Energy (DOE) became heavily involved in Internet research and started development of a successor to ARPANET. In the mid 1980s, all three of these branches developed the first Wide Area Networks based on TCP/IP. NASA developed the NASA Science Network, NSF developed CSNET and DOE evolved the Energy Sciences Network or ESNet.

More explicitly, NASA developed a TCP/IP based Wide Area Network, NASA Science Network (NSN), in the mid 1980s connecting space scientists to data and information stored anywhere in the world. In 1989, the DECnet-based Space Physics Analysis Network (SPAN) and the TCP/IP-based NASA Science Network (NSN) were brought together at NASA Ames Research Center creating the first multiprotocol wide area network called the NASA Science Internet, or NSI. NSI was established to provide a total integrated communications infrastructure to the NASA scientific community for the advancement of earth, space and life sciences. As a high-speed, multiprotocol, international network, NSI provided connectivity to over 20,000 scientists across all seven continents.

In 1984 NSF developed CSNET exclusively based on TCP/IP. CSNET connected with ARPANET using TCP/IP, and ran TCP/IP over X.25, but it also supported departments without sophisticated network connections, using automated dial-up mail exchange. This grew into the NSFNet backbone, established in 1986, and intended to connect and provide access to a number of supercomputing centers established by the NSF.

Transition towards an Internet

The term "Internet" was adopted in the first RFC published on the TCP protocol: (nternet Transmission Control Program, December 1974.)It was around the time when ARPANET was interlinked with NSFNet, that the term Internet came into more general use, with "an internet" meaning any network using TCP/IP. "The Internet" came to mean a global and large network using TCP/IP. Previously "internet" and "internetwork" had been used interchangeably, and "internet protocol" had been used to refer to other networking systems such as Xerox Network Services.

As interest in wide spread networking grew and new applications for it arrived, the Internet's technologies spread throughout the rest of the world. TCP/IP's network-agnostic approach meant that it was easy to use any existing network infrastructure, such as the IPSS X.25 network, to carry Internet traffic. In 1984, University College London replaced its transatlantic satellite links with TCP/IP over IPSS.

Many sites unable to link directly to the Internet started to create simple gateways to allow transfer of e-mail, at that time the most important application. Sites which only had intermittent connections used UUCP or FidoNet and relied on the gateways between these networks and the Internet. Some gateway services went beyond simple e-mail peering, such as allowing access to FTP sites via UUCP or e-mail.

TCP/IP becomes worldwide

The first ARPANET connection outside the US was established to NORSAR in Norway in 1973, just ahead of the connection to Great Britain. These links were all converted to TCP/IP in 1982, at the same time as the rest of the ARPANET.

CERN, the European Internet, the link to the Pacific and beyond

Between 1984 and 1988 CERN began installation and operation of TCP/IP to interconnect its major internal computer systems, workstations, PCs and an accelerator control system. CERN continued to operate a limited self-developed system CERNET internally and several incompatible (typically proprietary) network protocols externally. There was considerable resistance in Europe towards more widespread use of TCP/IP and the CERN TCP/IP intranets remained isolated from the Internet until 1989.

In 1988 Daniel Karrenberg, from CWI in Amsterdam, visited Ben Segal, CERN's TCP/IP Coordinator, looking for advice about the transition of the European side of the UUCP Usenet network (much of which ran over X.25 links) over to TCP/IP. In 1987, Ben Segal had met with Len Bosack from the then still small company Cisco about purchasing some TCP/IP routers for CERN, and was able to give Karrenberg advice and forward him on to Cisco for the appropriate hardware. This expanded the European portion of the Internet across the existing UUCP networks, and in 1989 CERN opened its first external TCP/IP connections. This coincided with the creation of Réseaux IP Européens (RIPE), initially a group of IP network administrators who met regularly to carry out co-ordination work together. Later, in 1992, RIPE was formally registered as a cooperative in Amsterdam.

At the same time as the rise of internetworking in Europe, ad hoc networking to ARPA and in-between Australian universities formed, based on various technologies such as X.25 and UUCPNet. These were limited in their connection to the global networks, due to the cost of making individual international UUCP dial-up or X.25 connections. In 1989, Australian universities joined the push towards using IP protocols to unify their networking infrastructures. AARNet was formed in 1989 by the Australian Vice-Chancellors' Committee and provided a dedicated IP based network for Australia.

The Internet began to penetrate Asia in the late 1980s. Japan, which had built the UUCP-based network JUNET in 1984, connected to NSFNet in 1989. It hosted the annual meeting of the Internet Society, INET'92, in Kobe. Singapore developed TECHNET in 1990, and Thailand gained a global Internet connection between Chulalongkorn University and UUNET in 1992.

Mobile phones and the Internet

The first mobile phone to have Internet connectivity was the Nokia 9000 Communicator, launched in Finland in 1996. The concept of a mobile phone based Internet did not take off until prices came down from that model and the network providers started to develop systems and services to enable the Internet on phones. NTT DoCoMo in Japan launched the first mobile Internet service, i-Mode in 1999 and this is considered the birth of the mobile phone based Internet. In 2001 the mobile phone based email system by Blackberry and its iconic phones were launched in America.

To make better use of the small screen and tiny keypad and one-handed operation typical of mobile phones, a simpler programming environment was created for the mobile phone Internet, called WAP for Wireless Application protocol. Most mobile phone Internet services operate on WAP.

The growth of the mobile phone based internet was initially a primarily Asian phenomenon with Japan, South Korea and Taiwan all soon finding the majority of their Internet users accessing by phone rather than by PC. Developing World countries followed next, with India, South Africa, Kenya, Philippines and Pakistan all reporting that the majority of their domestic Internet users accessed on a mobile phone rather than on a PC.

The European and North American use of the Internet was influenced by a large installed base of personal computers, and the growth of mobile phone Internet use was more gradual, but had reached national penetration levels of 20%-30% in most Western countries. In 2008 the cross-over happened, when more Internet access devices were mobile phones than personal computers. In many parts of the developing world, the ratio is as much as 10 mobile phone users to one PC user on the Internet.

Digital divide

While developed countries with technological infrastructures were joining the Internet, developing countries began to experience a digital divide separating them from the Internet. On an essentially continental basis, they are building organizations for Internet resource administration and sharing operational experience, as more and more transmission facilities go into place.

Africa
Asia and Oceania
Latin America

Africa

At the beginning of the 1990s, African countries relied upon X.25 IPSS and 2400 baud modem UUCP links for international and internetwork computer communications. In 1996 a USAID funded project, the Leland initiative, started work on developing full Internet connectivity for the continent. Guinea, Mozambique, Madagascar and Rwanda gained satellite earth stations in 1997, followed by Côte d'Ivoire and Benin in 1998.

Africa is building an Internet infrastructure. AfriNIC, headquartered in Mauritius, manages IP address allocation for the continent. As do the other Internet regions, there is an operational forum, the Internet Community of Operational Networking Specialists.

There are a wide range of programs both to provide high-performance transmission plant, and the western and southern coasts have undersea optical cable. High-speed cables join North Africa and the Horn of Africa to intercontinental cable systems. Undersea cable development is slower for East Africa; the original joint effort between New Partnership for Africa's Development (NEPAD) and the East Africa Submarine System (Eassy) has broken off and may become two efforts.

Asia and Oceania

The Asia Pacific Network Information Centre (APNIC), headquartered in Australia, manages IP address allocation for the continent. APNIC sponsors an operational forum, the Asia-Pacific Regional Internet Conference on Operational Technologies (APRICOT).

In 1991, the People's Republic of China saw its first TCP/IP college network, Tsinghua University's TUNET. The PRC went on to make its first global Internet connection in 1995, between the Beijing Electro-Spectrometer Collaboration and Stanford University's Linear Accelerator Center. However, China went on to implement its own digital divide by implementing a country-wide content filter.

Latin America

As with the other regions, the Latin American and Caribbean Internet Addresses Registry (LACNIC) manages the IP address space and other resources for its area. LACNIC, headquartered in Uruguay, operates DNS root, reverse DNS, and other key services.

Opening the network to commerce

The interest in commercial use of the Internet became a hotly debated topic. Although commercial use was forbidden, the exact definition of commercial use could be unclear and subjective. UUCPNet and the X.25 IPSS had no such restrictions, which would eventually see the official barring of UUCPNet use of ARPANET and NSFNet connections. Some UUCP links still remained connecting to these networks however, as administrators cast a blind eye to their operation.

During the late 1980s, the first Internet service provider (ISP) companies were formed. Companies like PSINet, UUNET, Netcom, and Portal Software were formed to provide service to the regional research networks and provide alternate network access, UUCP-based email and Usenet News to the public. The first dial-up on the West Coast, Best Internet, now Verio, opened in 1986. The first dialup ISP in the East was world.std.com, opened in 1989.

This caused controversy amongst university users, who were outraged at the idea of noneducational use of their networks. Eventually, it was the commercial Internet service providers who brought prices low enough that junior colleges and other schools could afford to participate in the new arenas of education and research.

By 1990, ARPANET had been overtaken and replaced by newer networking technologies and the project came to a close. In 1994, the NSFNet, now renamed ANSNET (Advanced Networks and Services) and allowing non-profit corporations access, lost its standing as the backbone of the Internet. Both government institutions and competing commercial providers created their own backbones and interconnections. Regional network access points (NAPs) became the primary interconnections between the many networks. The final commercial restrictions ended in May 1995 when the National Science Foundation ended its sponsorship of the Internet backbone."A Brief History of the Internet"

IETF and a standard for standards

The Internet has developed a significant subculture dedicated to the idea that the Internet is not owned or controlled by any one person, company, group, or organization. Nevertheless, some standardization and control is necessary for the system to function.

The liberal Request for Comments (RFC) publication procedure engendered confusion about the Internet standardization process, and led to more formalization of official accepted standards. The IETF started in January 1985 as a quarterly meeting of U.S. government funded researchers. Representatives from non-government vendors were invited starting with the fourth IETF meeting in October of that year.

Acceptance of an RFC by the RFC Editor for publication does not automatically make the RFC into a standard. It may be recognized as such by the IETF only after experimentation, use, and acceptance have proved it to be worthy of that designation. Official standards are numbered with a prefix "STD" and a number, similar to the RFC naming style. However, even after becoming a standard, most are still commonly referred to by their RFC number.

In 1992, the Internet Society, a professional membership society, was formed and the IETF was transferred to operation under it as an independent international standards body.

NIC, InterNIC, IANA and ICANN

The first central authority to coordinate the operation of the network was the Network Information Centre (NIC) at Stanford Research Institute (SRI) in Menlo Park, California. In 1972, management of these issues was given to the newly created Internet Assigned Numbers Authority (IANA). In addition to his role as the RFC Editor, Jon Postel worked as the manager of IANA until his death in 1998.

As the early ARPANET grew, hosts were referred to by names, and a HOSTS.TXT file would be distributed from SRI International to each host on the network. As the network grew, this became cumbersome. A technical solution came in the form of the Domain Name System, created by Paul Mockapetris. The Defense Data Network—Network Information Center (DDN-NIC) at SRI handled all registration services, including the top-level domains (TLDs) of .mil, .gov, .edu, .org, .net, .com and .us, root nameserver administration and Internet number assignments under a United States Department of Defense contract. In 1991, the Defense Information Systems Agency (DISA) awarded the administration and maintenance of DDN-NIC (managed by SRI up until this point) to Government Systems, Inc., who subcontracted it to the small private-sector Network Solutions, Inc.

Since at this point in history most of the growth on the Internet was coming from non-military sources, it was decided that the Department of Defense would no longer fund registration services outside of the .mil TLD. In 1993 the U.S. National Science Foundation, after a competitive bidding process in 1992, created the InterNIC to manage the allocations of addresses and management of the address databases, and awarded the contract to three organizations. Registration Services would be provided by Network Solutions; Directory and Database Services would be provided by AT&T; and Information Services would be provided by General Atomics.

In 1998 both IANA and InterNIC were reorganized under the control of ICANN, a California non-profit corporation contracted by the US Department of Commerce to manage a number of Internet-related tasks. The role of operating the DNS system was privatized and opened up to competition, while the central management of name allocations would be awarded on a contract tender basis.

Use and culture

E-mail and Usenet

E-mail is often called the killer application of the Internet. However, it actually predates the Internet and was a crucial tool in creating it. E-mail started in 1965 as a way for multiple users of a time-sharing mainframe computer to communicate. Although the history is unclear, among the first systems to have such a facility were SDC's Q32 and MIT's CTSS.

The ARPANET computer network made a large contribution to the evolution of e-mail. There is one report indicating experimental inter-system e-mail transfers on it shortly after ARPANET's creation. In 1971 Ray Tomlinson created what was to become the standard Internet e-mail address format, using the @ sign to separate user names from host names.

A number of protocols were developed to deliver e-mail among groups of time-sharing computers over alternative transmission systems, such as UUCP and IBM's VNET e-mail system. E-mail could be passed this way between a number of networks, including ARPANET, BITNET and NSFNet, as well as to hosts connected directly to other sites via UUCP. See the history of SMTP protocol.

From gopher to the WWW

As the Internet grew through the 1980s and early 1990s, many people realized the increasing need to be able to find and organize files and information. Projects such as Gopher, WAIS, and the FTP Archive list attempted to create ways to organize distributed data. Unfortunately, these projects fell short in being able to accommodate all the existing data types and in being able to grow without bottlenecks.

One of the most promising user interface paradigms during this period was hypertext. The technology had been inspired by Vannevar Bush's "Memex" and developed through Ted Nelson's research on Project Xanadu and Douglas Engelbart's research on NLS. Many small self-contained hypertext systems had been created before, such as Apple Computer's HyperCard. Gopher became the first commonly-used hypertext interface to the Internet. While Gopher menu items were examples of hypertext, they were not commonly perceived in that way.

In 1989, whilst working at CERN, Tim Berners-Lee invented a network-based implementation of the hypertext concept. By releasing his invention to public use, he ensured the technology would become widespread. For his work in developing the World Wide Web, Berners-Lee received the Millennium technology prize in 2004. One early popular web browser, modeled after HyperCard, was ViolaWWW.

Search engines

Even before the World Wide Web, there were search engines that attempted to organize the Internet. The first of these was the Archie search engine from McGill University in 1990, followed in 1991 by WAIS and Gopher. All three of those systems predated the invention of the World Wide Web but all continued to index the Web and the rest of the Internet for several years after the Web appeared. There are still Gopher servers as of 2006, although there are a great many more web servers.

As the Web grew, search engines and Web directories were created to track pages on the Web and allow people to find things. The first full-text Web search engine was WebCrawler in 1994. Before WebCrawler, only Web page titles were searched. Another early search engine, Lycos, was created in 1993 as a university project, and was the first to achieve commercial success. During the late 1990s, both Web directories and Web search engines were popular—Yahoo! (founded 1995) and Altavista (founded 1995) were the respective industry leaders.

By August 2001, the directory model had begun to give way to search engines, tracking the rise of Google (founded 1998), which had developed new approaches to relevancy ranking. Directory features, while still commonly available, became after-thoughts to search engines.

Database size, which had been a significant marketing feature through the early 2000s, was similarly displaced by emphasis on relevancy ranking, the methods by which search engines attempt to sort the best results first. Relevancy ranking first became a major issue circa 1996, when it became apparent that it was impractical to review full lists of results. Consequently, algorithms for relevancy ranking have continuously improved. Google's PageRank method for ordering the results has received the most press, but all major search engines continually refine their ranking methodologies with a view toward improving the ordering of results. As of 2006, search engine rankings are more important than ever, so much so that an industry has developed ("search engine optimizers", or "SEO") to help web-developers improve their search ranking, and an entire body of case law has developed around matters that affect search engine rankings, such as use of trademarks in metatags. The sale of search rankings by some search engines has also created controversy among librarians and consumer advocates.

Dot-com bubble

Suddenly the low price of reaching millions worldwide, and the possibility of selling to or hearing from those people at the same moment when they were reached, promised to overturn established business dogma in advertising, mail-order sales, customer relationship management, and many more areas. The web was a new killer app—it could bring together unrelated buyers and sellers in seamless and low-cost ways. Visionaries around the world developed new business models, and ran to their nearest venture capitalist. Of course some of the new entrepreneurs were truly talented at business administration, sales, and growth; but the majority were just people with ideas, and didn't manage the capital influx prudently. Additionally, many dot-com business plans were predicated on the assumption that by using the Internet, they would bypass the distribution channels of existing businesses and therefore not have to compete with them; when the established businesses with strong existing brands developed their own Internet presence, these hopes were shattered, and the newcomers were left attempting to break into markets dominated by larger, more established businesses. Many did not have the ability to do so.

Worldwide Online Population Forecast

In its "Worldwide Online Population Forecast, 2006 to 2011," JupiterResearch anticipates that a 38 percent increase in the number of people with online access will mean that, by 2011, 22 percent of the Earth's population will surf the Internet regularly.

JupiterResearch says the worldwide online population will increase at a compound annual growth rate of 6.6 percent during the next five years, far outpacing the 1.1 percent compound annual growth rate for the planet's population as a whole. The report says 1.1 billion people currently enjoy regular access to the Web.

North America will remain on top in terms of the number of people with online access. According to JupiterResearch, online penetration rates on the continent will increase from the current 70 percent of the overall North American population to 76 percent by 2011. However, Internet adoption has "matured," and its adoption pace has slowed, in more developed countries including the United States, Canada, Japan and much of Western Europe, notes the report.

As the online population of the United States and Canada grows by about only 3 percent, explosive adoption rates in China and India will take place, says JupiterResearch. The report says China should reach an online penetration rate of 17 percent by 2011 and India should hit 7 percent during the same time frame. This growth is directly related to infrastructure development and increased consumer purchasing power, notes JupiterResearch.

By 2011, Asians will make up about 42 percent of the world's population with regular Internet access, 5 percent more than today, says the study.

Penetration levels similar to North America's are found in Scandinavia and bigger Western European nations such as the United Kingdom and Germany, but JupiterResearch says that a number of Central European countries "are relative Internet laggards."

Brazil "with its soaring economy," is predicted by JupiterResearch to experience a 9 percent compound annual growth rate, the fastest in Latin America, but China and India are likely to do the most to boost the world's online penetration in the near future.

For the study, JupiterResearch defined "online users" as people who regularly access the Internet by "dedicated Internet access" devices. Those devices do not include cell phones.

11) HISTORY OF THE " GUI"

2009-06-19T14:15:00.000-07:00

The graphical user interface (GUI), understood as the use of graphic icons and a pointing device to control a computer, has over the last four decades a steady history of incremental refinements built on some constant core principles. Several vendors have created their own windowing systems based on independent code but sharing the same basic elements that define the WIMP paradigm. There have been important technological achievements and enhancements to the general interaction were given in small steps over previous systems and there have been a few significant breakthroughs in terms of use, but the same organizational metaphors and interaction idioms are still in use.

Initial developments

Early dynamic information devices such as radar displays, where input devices where used for direct control of computer-created data, set the basis for later improvements of graphical interfaces.

The concept of a windowing system was introduced by the first real-time graphic display systems for computers: the SAGE Project and Ivan Sutherland's Sketchpad.

Augmentation of Human Intellect (NLS)

Doug Engelbart's Augmentation of Human Intellect project at SRI in the 1960s developed the On-Line System (NLS), which incorporated a mouse-driven cursor and multiple windows used to work on hypertext. Engelbart had been inspired, in part, by the memex desk based information machine suggested by Vannevar Bush in 1945. Much of the early research was based on how young humans learn.

Xerox PARC

Engelbart's work directly led to the advances at Xerox PARC. Several people went from SRI to Xerox PARC in the early 1970s. In 1973 Xerox PARC developed the Xerox Alto personal computer. It was the first computer to use the desktop metaphor and graphical user interface (GUI). It was not a commercial product, but several thousand units were built and were heavily used at PARC and at several universities for many years. The Alto greatly influenced the design of personal computers in the following decades, notably the Macintosh and the first Sun workstations.

In 1974, work began on Gypsy, the first bitmap What-You-See-Is-What-You-Get (WYSIWYG) cut & paste editor. In 1975, Xerox engineers demonstrated a Graphical User Interface "including icons and the first use of pop-up menus".

The 80s: Early commercial developments

Apple Lisa and Macintosh (and later, the Apple IIgs)

Short for Graphical User Interface, the GUI was first developed at Xerox PARC by Alan Kay, Douglas Engelbart, and a group of other researchers. A GUI uses windows, icons, and menus to carry out commands such as opening files, deleting files, moving files, etc. and although many GUI Operating Systems are operated by using a mouse, the keyboard can also be used by using keyboard shortcuts or arrow keys.

Beginning in 1979, started by Steve Jobs and led by Jef Raskin, the Lisa and Macintosh teams at Apple Computer (which included former members of the Xerox PARC group) continued to develop such ideas. The Macintosh, released in 1984, was the first commercially successful product to use a GUI. A desktop metaphor was used, in which files looked like pieces of paper; directories looked like file folders; there were a set of desk accessories like a calculator, notepad, and alarm clock that the user could place around the screen as desired; and the user could delete files and folders by dragging them to a trash can on the screen. Drop down menus were also introduced.

There is still some controversy over the amount of influence that Xerox's PARC work, as opposed to previous academic research, had on the GUIs of Apple's Lisa and Macintosh, but it is clear that the influence was extensive, because first versions of Lisa GUIs even lacked icons. These prototype GUIs are at least mouse driven, but completely ignored the WIMP concept.Note also that Apple was invited by PARC to view their research, and a number of PARC employees subsequently moved to Apple to work on the Lisa and Macintosh GUI. However, the Apple work extended PARC's considerably, adding manipulatable icons and a fixed menu bar and direct manipulation of objects in the file system.

In 1986 the Apple IIgs was launched, a very advanced model of the Apple II successful series, based on 16-bit technology (in fact, virtually two machines into one). It came with a new operating system, the Apple GS/OS, which features a Finder-like GUI, very similar to that of the Macintosh series, able to deal with the advanced graphic abilities of its Video Graphics Chip (VGC).

Graphical Environment Manager (GEM)

Digital Research (DRI) created the Graphical Environment Manager as an add-on program for personal computers. GEM was developed to work with existing CP/M and MS-DOS operating systems on business computers such as IBM-compatibles. It was developed from DRI software, known as GSX, designed by a former PARC employee. The similarity to the Macintosh desktop led to a copyright lawsuit from Apple Computer, and a settlement which involved some changes to GEM. This was to be the first of a series of 'look and feel' lawsuits related to GUI design in the 1980s.

GEM received widespread use in the consumer market from 1985, when it was made the default user interface built in to the TOS operating system of the Atari ST line of personal computers. It was also bundled by other computer manufacturers and distributors, such as Amstrad. Later, it was distributed with the best-selled Digital Research version of DOS for IBM PC compatibles, the DR-DOS 6.0. The GEM desktop faded from the market with the withdrawal of the Atari ST line in 1992 and with the popularity of the Microsoft Windows 3.0 in the PC front by the same years.

DeskMate

Tandy's DeskMate appeared in the early 1980's on its TRS-80 machines and was ported to its Tandy 1000 range in 1984. Like most PC GUIs of the time it depended on MS-DOS. The application was popular at the time and included a number of programs like Draw, Text and Calendar as well as attracting outside investment such as Lotus 1-2-3 for DeskMate.

Amiga Intuition and the Workbench

Due to a mistake made by the Commodore sales department, the first floppies of AmigaOS which were released with Amiga1000 named the whole OS "Workbench". Since then, users and CBM itself referred to "Workbench" as the nickname for the whole AmigaOS (including Amiga DOS, Extras, etc.). This common consent ended with release of version 2.0 of AmigaOS, which re-introduced proper names to the installation floppies of AmigaDOS, Workbench, Extras, etc.).

Early versions of AmigaOS did treat the Workbench as just another window on top of a blank screen, but this is due to the ability of AmigaOS to have invisible screens with a chromakey or a genlock - one of the most advanced features of Amiga platform - even without losing the visibility of Workbench itself. In later AmigaOS versions Workbench could be set as a borderless desktop.

Amiga users were able to boot their computer into a command line interface (aka. CLI/shell). This was a keyboard-based environment without the Workbench GUI. Later they could invoke it with the CLI/SHELL command LoadWB which performs the task to load Workbench GUI.

Like most GUIs of the day Amiga's Intuition followed Xerox, and sometimes Apple's lead, but a CLI was included which dramatically extended the functionality of the platform, but Cli/Shell of Amiga is not just a simple text based interface like in MS-DOS but it is another graphic process driven by Intuition engine and with same gadgets included in Amiga graphics.library and serving the GUI process and CLI/Shell interface integrates itself with the Workbench, sharing the same privileges with the GUI.
The Amiga computer was launched by Commodore in 1985 with a GUI called Workbench based on an internal engine which drives all the input events called Intuition, and developed almost entirely by RJ Mical. The first versions used a blue/orange/white/black default palette, which was selected for high contrast on televisions and composite monitors. Workbench presented directories as drawers to fit in with the "workbench" theme. Intuition was the widget and graphics library that made the GUI work. It was driven by user events through the mouse, keyboard, and other input devices.

MS-DOS file managers and utility suites

Because most of the very early IBM PC and compatibles lacks any common true graphical capability (they only shared the 80-column basic text mode compatible with the original MDA display adapter), a series of file managers arose, including Microsoft's DOS Shell, which features typical GUI elements as menus, push buttons, lists with scrollbars and mouse pointer. The name Text user interface was later invented to name this kind of interface. Many MS-DOS text mode applications, like the default text editor for MS-DOS 5.0 (and related tools, like QBasic), also shared the same philosophy. The IBM DOS Shell included with IBM DOS 5.0 (circa 1992) supported both text display modes and actual graphics display modes, making it both a TUI and a GUI, depending on the chosen mode.

Advanced file managers for MS-DOS were able to redefine character shapes with EGA and better display adapters, giving some basic low resolution icons and graphical interface elements, including an arrow (instead of a coloured cell block) for the mouse pointer. When the display adapter lacks the ability to change the character's shapes, they default to the CP437 character set found in the adapter's ROM. Some popular utility suites for MS-DOS, as Norton Utilities (pictured) and PC Tools used these techniques as well.

DESQview was a text mode multitasking program introduced in July 1985. Running on top of MS-DOS, it allowed users to run multiple DOS programs concurrently in windows. It was the first program to bring multitasking and windowing capabilities to a DOS environment in which existing DOS programs could be used. DESQview was not a true GUI but offered certain components of one, such as resizable, overlapping windows and mouse pointing.

Applications under MS-DOS with proprietary true GUIs

To take the maximum advantage possible in lack of a true common GUI under MS-DOS, the most of the graphical applications which worked with EGA, VGA and better graphic cards had proprietary built-in GUIs, before the MS-Windows age. One of the best known was Deluxe Paint, a popular painting software with a typical WIMP interface.

The original Adobe Acrobat Reader executable file for MS-DOS was able to run on both the standard Windows 3.x GUI and the standard DOS command prompt. When it was launched from the command prompt, it provides its own true GUI (on VGA), which provides the full of its functionality to read PDF files.

Microsoft Windows (16-bit versions)

Windows 1.0 was a GUI for the MS-DOS operating system that had been the OS of choice for IBM PC and compatible computers since 1981. Windows 2.0 followed, but it wasn't until the 1990 launch of Windows 3.0, based on Common User Access that its popularity truly exploded. The GUI has seen minor redesigns since, mainly the networking enabled Windows 3.11 and its Win32s 32-bit patch. The 16-bit line of MS Windows were discontinued with the introduction of Windows 95 and Windows NT 32-bit based architecture in the 1990's.

The main window of a given application can occupy the full screen in maximized status. The users must then to switch between maximized applications using the Alt+Tab keyboard shortcut; no alternative with the mouse except for de-maximize. When none of the running application windows is maximized, switching can be done by clicking on a partially visible window, as is the common way in other GUIs.

In 1988, Apple sued Microsoft for copyright infringement of the LISA and Apple Macintosh GUI. The court case lasted 4 years before almost all of Apple's claims were denied on a contractual technicality. Subsequent appeals by Apple were also denied. Microsoft and Apple apparently entered a final, private settlement of the matter in 1997.

GEOS

GEOS was launched in 1986. Originally written for the 8-bit home computer Commodore 64 and shortly after, the Apple II series it was later ported to IBM PC systems. It came with several application programs like a calendar and word processor, and a cut-down version served as the basis for America Online's DOS client. Compared to the competing Windows 3.0 GUI it could run reasonably well on simpler hardware. But it was targeted at 8-bit machines and the 16-bit computer age was dawning.