3.1 Computer Classification.
To classify computers we can use many different types of methods. Main method will be computer generations. Under computer generations we can see five generations classified under technical terms that use on the computers.
1) 1st Generation (1940-1956) – Used vacuum tubes.
2) 2nd Generation (1956-1963) – Used transistors.
3) 3rd Generation (1964-1971) – Used integrated circuits(IC).
4) 4th Generation (1972-2010) – Used microchip or central processing unit (CPU).
5) 5th Generation (2010 and Beyond) – Artificial intelligence (AI).

1) 1st Generation (1940-1956).
First generation of computers began with using vacuum tubes as the basic components for memory and hardware, and was regularly huge, taking up whole rooms. These computers were extremely costly to work and notwithstanding using a lot of power, the main computers produced a considerable measure of heat, which was frequently the reason for breakdowns. These original computers depended on “machine language”. These computers were restricted to taking care of one issue at any given moment. It would take operators days or even a long time to set-up another issue. Input depended on punched cards and paper tape, Output was shown on printouts. The two eminent machines of this period were the UNIVAC and ENIAC machines. The UNIVAC was the first business computer, it conveyed to a business customer, the U.S. Statistics Bureau in 1951. The ENIAC was produced by Army Ordnance to process World War II ballistic terminating tables. It measured 30 tons and used 200 kilowatts of electric power.

UNIVAC computer at the Census Bureau
? Advantages
• Vacuum tubes were the only electronic component available this period.

? Disadvantages
• The size of computers was very large.
• Computers depended on only machine language.
• The computers heated very soon.
2) 2nd Generation (1956-1963).
This generation using the transistors for replacing vacuum tubes, the transistors first invented in 1947 at Bell Labs. Transistors weren’t used significantly in computers until the end of the 1950s.In any case they were better than the vacuum tubes, making computers smaller, faster, cheaper and less heavy on electricity use. More reliable and more energy-efficient, than first-generation predecessors, the language evolved from cryptic binary language to symbolic (Assembly) languages. They still relied on punched cards for input and printouts for output.

? Advantages
• Smaller than first generation computers.
• Accuracy improved.
• Computers were more reliable.

? Disadvantages
• Still using punch cards for input.
• Cooling system was required.
• Can be used for only specific purposes.

3) 3rd Generation (1964-1971).
Third generation of computers developed by the integrated circuits, a single integrated circuit has many transistors, resistors and capacitors along with the associated circuitry. By this phase, transistors were now being miniaturized and placed on silicon chips, called semiconductors. This generation massive increased the speed and efficiency of these computers. These were the first computers where users interacted using keyboards and monitors who interfaced with an operating system, a significant leap up from the punch cards and printouts. As a result of these advances third generation computers became cheaper and smaller than their predecessors.
? Advantages
• Smaller in size as compared two previous generations.
• More reliable than previous generations.

• Less expensive.
• Used mouse and keyboard for input.

? Disadvantages
• Air conditioning was required.
• Exceedingly modern technology required for the assembling of IC chips.

4) 4th Generation (1972-2010)
The fourth generation computers started with the invention of microprocessor, as thousands of integrated circuits were built onto a single silicon chip. Ted Hoff produced the first microprocessor in 1971 for Intel. It was known as Intel 4004.The year 1981 IBM Company was designed first computer for home use.1984 saw the Macintosh introduced by Apple. Examples for the fourth generation computers are Apple Macintosh and IBM computers. The size of latest Microprocessors is usually one square inch. It can contain millions of electronic circuits. Latest Microprocessors manufacturing companies are Intel, AMD, and Apple.
? Advantages
• More powerful and reliable than all previous generations.
• General purpose.
• No air conditioning required.

• Smaller in size as compared all previous generations.

? Disadvantages
• Exceedingly modern technology required for the assembling of Microprocessor.
5) 5th Generation (2010 and Beyond)
Fifth generation computing devices, based on artificial intelligence, still scientists are working hard on it. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. They are trying to create a computer with real IQ with the help of advanced programming and technologies. IBM Watson computer is one example for that. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization. The advancement in modern technologies will revolutionize the computer in future.