Generations of computers

The subsequent development of computers is usually described as occurring in generations. The first generation, which began with Eckert and Mauchly's ENIAC, is considered to span the period 1946-1959. This generation of computers is characterized by the use of vacuum tubes in the CPU and internal memory units, the first commercial computers, and many fundamental advances in computing. The first commercial computer was the UNIVAC 1 (UNIVersal Automatic Computer), which was sold to the Census Bureau in 1951.

In the second generation of computers, 1959-1964, the vacuum tube was replaced by the transistor. The transistor, a solid-state device, was the major breakthrough that allowed computers to have reasonable size and power. A solid-state device is made of minerals so that it can be instructed to allow or not allow a flow of current. Because solid-state devices did not use the hot filament that was in vacuum tubes, the use of transistors reduced the computer's heat output and power requirement. Transistors also increased the reliability of the computer, because they did not burn out the way vacuum tubes did. This breakthrough in turn reduced the cost of owning and operating a computer. This period saw tremendous growth in the use of computers by government, business, and industry.

The introduction of the integrated circuit in 1965 was the beginning of the third generation of computers. With this technological advance, an entire circuit board containing transistors and connecting wires could be placed on a single chip. This development meant greater reliability and compactness combined with low cost and power requirements. During this period, IBM controlled the mainframe market with its 360 (later to be 370) series of computers. This series was so well designed and built that its successors are still in heavy use today.

The fourth and current generation of computers began in 1971 with the introduction of the microprocessor—a central processing unit on a chip. This generation includes the introduction of supercomputers. These "monster computers" are in heavy demand for military and meteorological applications that require a high speed of operation. Another important advance of this generation has been the introduction of the personal computer, because the power of the computer has been made available to anybody who wishes to use one.

A possible "fifth generation" of computers has recently been discussed in the media. The Japanese government has a broad-ranging plan to leapfrog American superiority in hardware with a fifth-generation computer that will include parallel processors—several CPUs working in parallel to speed up execution time. No one knows how successful this particular plan will be, but we probably won't have to wait long to find out.

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