Sarah Dow

History of computing

Way back in early history, when people relied mainly on their brains to perform calculations, people used their fingers, pebbles, and tally sticks for computing purposes.

Various attempts were made to build general-purpose programmable computers from the same mechanical devices used in calculators. But the problems posed by the lack of technology at the time were not satisfactorily solved until the introduction of electronic computing techniques in the mid-20th century.   Between Pascal's invention and around 1820 there were about 25 manufacturers of calculating machines; most of them were the work of one man.  Few of them worked correctly and even less actually reached the manufacturing line.

In the mid-19th century Charles Babbage, a visionary British mathematician at Cambridge University, designed the first computers to perform multistep operations automatically.

The technologies were entirely mechanical. He called this first computing machine the Difference Engine, and it was intended to compute and print mathematical tables automatically. The Difference Engine performed only one arithmetic operation: addition. Babbage constructed a small portion of his first Difference Engine in 1832, which served as a demonstration prototype.

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The first widely known general-purpose electronic computer was the Electronic Numerical Integrator and Calculator (ENIAC) that John W. Mauchly and J. Presper Eckert built at the University of Pennsylvania.

The primary motivation for the ENIAC was the need to construct ballistic tables for the U.S. Army. Work began on the ENIAC in 1943 and in 1946 it was completed. It was an enormous machine weighing about 30 tons and filling a 30 by 50 foot room. It contained 1,500 electromechanical relays and over 18,000 vacuum tubes and when it was switched on it consumed 150,000 watts of energy. Despite its enormous size ...

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