Perhaps the earliest device for working out sums was the abacus. This began as a clay tablet into which grooves were cut. Pebbles were then placed or taken away from grooves to perform addition and subtraction. (Our word calculation comes from the Latin word calculus meaning 'pebble').

Because the pebbles were likely to become mislaid, they were later replaced by beads threaded on to wires and mounted in a frame. By moving the beads backwards and forwards, addition, subtraction, division and multiplication could be done. In 1614 John Napier, an astronomer, invented a ready-reckoned, known as Napier's bones, to help him make complex calculations accurately. From this was developed in 1621 the earliest form of the slide rule.

The first…show more content… These circuits are mainly used for solving a wide variety of complex engineering problems, like investigation of stresses in aircraft, ships and large engineering structures. They can also be used to simulate and set up models of complex installations and study the effect of various operational factors on the complex installations.

They can for example, be used to simulate the behavior of an aircraft in response to the actions of crew members. Using analog computers, apparent equipment failures or other emergencies can be introduced for proper training of the crew. The first automatic analog computer designed to solve complex differential equations, was described in detail in 1876 by the English Scientist William Thomson.

Digital Computers: These are used in commerce and industry for extensive arithmetical calculations which would otherwise require enormous clerical effort. Such computers carry out mathematical operations with the variables expressed in the computer as numbers, usually in the binary system (given below).

These numbers are recorded in the computer electronically, as a series of temporary magnets, each magnetized in one of the two possible directions. The two magnetization direction corresponds two numbers of the binary system.

The first electronic digital computer, known as the Electronic Numerical Integrator and Computer or NIIAC was developed at the University of Pennsylvania in 1947 by