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Alan Turing

(1912—1954) mathematician and computer scientist

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British mathematician, who introduced the concept of the Turing machine.

Born in London, he was educated at King's College, Cambridge, where he was elected to a fellowship in 1936. In the following year he published On Computable Numbers, a work that quickly gained him a worldwide reputation and introduced into mathematics the notion of a Turing machine. Turing's work derived from the 23rd problem posed (in 1900) by David Hilbert, i e how to decide whether the propositions of predicate logic are true or false – the Entscheidungsproblem. Turing described a universal machine capable of modelling the process of computation. It would consist of no more than a continuous tape divided into cells. The machine would be capable of moving the tape to the left and to the right, to halt it, to print the numbers 0 and 1, and to erase. Turing was able to show that there are noncomputable functions. He was further able to link this result with first-order logic and so demonstrate that predicate logic was essentially undecidable.

With the outbreak of World War II Turing found himself at Bletchley Park, where he worked on deciphering the German Enigma codes. Although much remains to be written of this period it appears that Turing's work on the project was vital and that few individuals, of whatever rank, made a greater contribution to the final Allied victory. It was also work that demonstrated the importance of computers in solving otherwise intractable problems. Turing, in no sense an abstract mathematician, was aware of both the theoretical potentialities and the engineering constraints of a computing machine and consequently sought ways to develop and promote his concept of the modern computer. After the war (1945) he therefore joined the staff of the National Physical Laboratory at Teddington to work on the development of ACE (Automatic Computing Engine). However, without the discipline imposed by war Turing found it impossible to submit to the bureaucratic procedures of the civil service and in 1948 moved to Manchester University to work on MADAM (Manchester Automatic Digital Machine). While there he published his widely read paper Computing Machinery and Intelligence (1950), in which he invited his readers, unsuccessfully he predicted, to propose ways to distinguish between computers and intelligent minds.

With sufficient backing Turing could well have helped establish a soundly based computer industry in Britain in the 1950s. As it turned out, he was charged with, by the standards of the day, a minor homosexual offence, which led to his suicide. He died by sucking on an orange he had previously injected with cyanide.

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