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Alan Turing

Alan Mathison Turing (23 June,1912 - 7 June, 1954) was an English mathematician, logician and cryptographer.

Turing is often considered to be the father of modern computer science. He provided an influential formalization of the concept of the algorithm and computation with the Turing machine.

He made a significant and characteristically provocative contribution to the debate regarding artificial intelligence: whether it will ever be possible to say that a machine is conscious and can think.

He later worked at the National Physical Laboratory, creating one of the first designs for a stored-program computer, the ACE.

In 1948, he moved to the University of Manchester to work on the Manchester Mark 1, then emerging as one of the world's earliest true computers.

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World War II

During the Second World War, Turing was a main participant in the efforts at Bletchley Park to break German ciphers. Building on cryptanalysis work carried out in Poland by Marian Rejewski, he contributed several insights into breaking both the Enigma machine and the Lorenz SZ 40/42, and was, head of Hut 8, the section responsible for reading German naval signals.

Turing-Welchman Bombe

Turing designed an electromechanical machine to help break Enigma faster than bomba. The bombe, with an enhancement suggested by mathematician Gordon Welchman, became one of the primary tools, and the major automated one, used to attack Enigma-protected message traffic.

The bombe detected when a contradiction had occurred, and ruled out that setting, moving onto the next. Most of the possible settings would cause contradictions and be discarded, leaving only a few to be investigated in detail. Turing's bombe was first installed on 18 March 1940. Over two hundred bombes were in operation by the end of the war.

Hut 8 and Naval Enigma

Turing solved the naval Enigma indicator system, which was more mathematically complex than the indicator systems used by the other services. Turing also invented a Bayesian statistical technique termed "Banburismus" to assist in breaking Naval Enigma. Banburismus could rule out certain orders of the Enigma rotors, reducing time needed to test settings on the bombes.

Turing devised a technique termed Turingismus for use against the Lorenz cipher used in the Germans' new Geheimschreiber machine which was one of those codenamed "Fish". Turing travelled to the United States in November 1942 and worked with U.S. Navy cryptanalysts on Naval Enigma and bombe construction in Washington, and assisted at Bell Labs with the development of secure speech devices.

In the latter part of the war, while teaching himself electronics at the same time, and assisted by engineer Donald Bailey, Turing undertook the design of a portable machine codenamed Delilah to allow secure voice communications. It was intended for different applications, lacking capability for use with long-distance radio transmissions, and in any case, Delilah was completed too late to be used during the war.

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Early Computers and The Turing Test

From 1945 to 1947, Turing was at the National Physical Laboratory where he worked on the design of the Automatic Computing Engine (ACE). He presented a paper in 1946, which was the first detailed design of a stored-program computer. Although ACE was a feasible design, the secrecy surrounding the wartime work at Bletchley Park led to delays in starting the project and he became disillusioned.

In 1948 he was appointed Reader in the Mathematics Department at Manchester and in 1949 became deputy director of the computing laboratory at the University of Manchester, and worked on software for one of the earliest true computers - The Manchester Mark 1.

During this time he continued to do more abstract work, and in "Computing machinery and intelligence", Turing addressed the problem of artificial intelligence, and proposed an experiment now known as the Turing test, an attempt to define a standard for a machine to be called "intelligent". The idea was that a computer could be said to "think" if it could fool an interrogator into thinking that the conversation was with a human.

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Prosecution and Death

Homosexuality was illegal in the United Kingdom and regarded as a mental illness and subject to criminal sanctions. In 1952, Arnold Murray, a 19-year-old recent acquaintance of Turing's, helped an accomplice to break into Turing's house, and Turing reported the crime to the police. As a result of the police investigation, Turing acknowledged a sexual relationship with Murray.

Turing was given a choice between imprisonment and probation, conditional on his undergoing hormonal treatment designed to reduce libido. He accepted the estrogen hormone injections, which lasted for a year, to avoid jail.

On 8 June 1954, his cleaner found him dead. The previous day, he had died of cyanide poisoning, apparently from a cyanide-laced apple he left half-eaten beside his bed. The apple itself was never tested for contamination with cyanide, but a post-mortem established that the cause of death was cyanide poisoning. Most believe that his death was intentional, and the death was ruled a suicide.

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