Alan Turing (1912–1954) was the som of an English civil servant that worked in India. He attended boarding school at Sherbourne followed by a stint at Cambridge University. While there he studied mathematics under Newman, a professor whose interest lay in the field of mathematical logic. He became acquainted with two important papers published by the Austrian logician Kurt Gödel that were published around 1930 in the same field, which was an active one at the time. The subject of the papers was the Hilbert, or "decision" problem, asks if there is a given finite procedure to determine if a given Diophantine equation is solvable. After Cambridge, Turing went to Princeton University as it was the principal location where research into mathematical logic was occurring. In 1936 Turing presented a model of computing known as the "Turing Machine", which along with Gödel's 1931 "Incompleteness Theorem" was an extremely important negative result in mathematics. Other important results in the area were obtained by Alonzo Church and Post.
In 1939 the Second World War broke out and Turing became involved in classified deciphering efforts at Bletchley Park in the United Kingdom. Through analysis of a ciphering machine used by the Germans, known as the Enigma cipher, that was captured by the Polish military, he was able to break the cipher. This had profound military implications and altered the course of the war to the favour of the Allies. Due to the exigencies of war it was necessary to crack ciphertext quickly; decrypting the contents of a message containing the time and location of an attach is not useful after the fact.
At Bletchly the Colossus decoding machine was built to assist in decoding ciphertext. The engineering expertise gained in it's construction was later applied to the development of computers. After the war, Turing returned to Cambridge in order to work on computing until 1948. He then left for the University of Manchester where he remained until he committed suicide in 1952.
Aside: the first real stored-program computer in Canada, a Ferret model, was obtained by the University of Toronto from the University of Manchester in 1950.
Turing also worked on:
- Artificial intelligence (1950 paper described the so-called Turing Test)
- Theoretical computation
Cf. the biography of Turing written by Hodge, a British mathematician active in the gay rights movement, as well as the film Breaking the Code.