A computer is a programmable, usually electronic, device. The modern computer is generally accepted to have been invented during the 19th century by the mathematician Charles Babbage.
Computers are of two distinct types: analog and digital. Analog computers operate by manipulating electrical potentials, voltage in simple terms. Digital computers operate on fixed values, usually the binary code of one and zero. Modern computers are generally digital, and certainly all personal computers are digital.
Early digital computers used electrical relays as their two-state (binary) devices - two-state, they were either 'on' or 'off'. These early digital computers were first made during the 1940's, were large and were used for military purposes and in a few research laboratories. They were unreliable due to the unreliability of the physical contacts of the relays, and were very low speed - compared to modern computers. During the 1950's valves or vacuum tubes replaced relays in digital computers, and by the 1960's they in turn were replaced by transistors - enabling a computer with the power of one which filled a room in the 1950's to be built which would fit in a shoe box. Transistors were in turn replaced by the integrated circuit or 'silicon chip', allowing computers to be made even smaller and smaller.
In 1980 Sir Clive Sinclair revolutionised computing with the invention of the ZX80 domestic micro computer, and a year later marketed the ZX81, the first computer to be built with just four siliconchips. Shortly afterwards the personal computer or PC emerged aimed at the business market. Research Computer
Abbreviations
SciTech
Research Computer