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Unit 2: Generation of Computers

2.1 History of Computers
Notes
History of computers begins with the invention of the abacus in 3000 BC, followed by the invention
of mechanical calculators in 1617. The years beyond 1642 till 1980 are marked by inventions of
zeroth, first, second and third generation computers. The years beyond 1980 till today, are marked
by fourth generation computers. Fifth generation computers are still under research and
development.

2.1.1 Earlier Computing Devices (3000 BC–1617 AD)

Abacus is a rudimentary first computing device developed in 3000 BC. It consists of a row of wires
held in a wooden frame having beads stung on them as shown in Figure 2.1. It is used for calculations
by sliding the heads along the wires.

Figure 2.1: The Abacus—First Computing Device

In 1617, John Napier, a Scottish mathematician invented a mechanical calculator
called the ‘Napier’s bones’. He devised a set of eleven rods each having four faces.
As these rods were carved from bones, therefore they were called Napier’s bones.
The rods were used to find products and quotients of large numbers. John Napier
also introduced logarithms.

2.1.2 Zeroth Generation Computers (1642–1946)

The zeroth generation of computers (1642–1946) was marked by the invention of mainly mechanical
computers. Pascaline was the first mechanical device, invented by Blaise Pascal, a French
mathematician in 1642. In this machine, numbers were entered, by dialing a series of number wheels.
A series of toothed wheels transferred the movements to a dial and hence showed the results. In

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