Second Generation Computers : Transistors replaced the Vacuum
Tubes in the second generation computers. Transistors are too much smaller,
cheaper and produce very low heat as compared to vacuum tubes. One of the main
computer of this time was IBM 700 series.
Third Generation Computers : Integrated Circuits started the
third generation of computers. In an integrated circuit the components such as
transistors, resistors and conductors are fabricated on semiconductor material
such as silicon. Thus, a desired circuit can be fabricated in a tiny piece of
silicon rather than assembling several discrete components into the same
circuit. Hundreds or even thousands of transistors could be fabricated on a
single wafer of silicon. In addition, these fabricated transistors can be
connected with a process of metalisation to form logic circuits on the same
chip they have been produced.
Fourth Generation computers : Very large scale integration
(VLSI) where thousands of transistors can be integrated on a single chip. The
main impact of VLSI was that, it was possible to produce a complete CPU or main
memory or other similar devices on a single IC chip. This implied that mass
production of CPU, memory etc. can be done at a very low cost. The VLSI based
computer architecture is sometimes referred to as fourth generation computers.
