Page 10 - Handout Digital Electronics

Figure 5: Image of an integrated circuit

Features of third generation computers

• They used Integrated Circuit (IC) chips in place of the transistors.
• Semi-conductor memory devices were used.
• The size was greatly reduced, the processing speed was high, and they were more accurate
and reliable.
• Large Scale Integration (LSI) and Very Large-Scale Integration (VLSI) were also developed.
• The minicomputers were introduced in this generation.
• They used high level language for programming.

Most popular examples of this generation are IBM 360, IBM 370 and others.

1.5 Fourth Generation (1971-1980)
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The 4 generation computers were developed using Large Scale Integrated circuits (LSIs). An IC
containing about 100 components is called LSI (Large Scale Integration) and the one, which has more
than 1000 such components, is called VLSI (Very Large-Scale Integration). It uses large scale Integrated
Circuits (LSIC) built on a single silicon chip called microprocessors. This chip (Intel 4004) developed by
Intel in 1971, helped with the reduction of the size of the computer. Due to the development of a
microprocessor, it is possible to place a computer’s central processing unit (CPU), memory and
input/out controls on a single chip (Burns, D. n.d. The five generations of computers,
www.btob.co.nz).These computers are called microcomputers. Later very large-scale Integrated
Circuits (VLSIC) replaced LSICs. So, a computer which was occupying a very large room in earlier days
could now be placed on a table.

Figure 6: Very Large-Scale Integration (VLSI)

The personal computer (PC) that we now see in our schools or at our homes are fourth generation
computers. The main memory used fast semiconductors chips with a capacity of up to 4 MB. Hard disks
were used as secondary memory. Keyboards, dot matrix printers etc. were developed. Operating
systems such as MS-DOS, UNIX, and Apple’s Macintosh were available. Object oriented language, C++
and others were developed.

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