Alan Mathison Turing

Alan Mathison Turing (June 23, 1912–June 7, 1954) was a British mathematician, logician, and cryptographer, and is considered to be one of the fathers of modern computer science. He provided an influential formalisation of the concept of algorithm and computation: the Turing machine. He formulated the now widely accepted 'Turing' version of the Church-Turing thesis, namely that any practical computing model has either the equivalent or a subset of the capabilities of a Turing machine. During World War II he worked on breaking German cyphers, particularly the Enigma machine; he was the director of the Naval Enigma section at Bletchley Park for some time. After the war, he designed one of the earliest electronic programmable digital computers at the National Physical Laboratory and, shortly thereafter, actually built another early machine at the University of Manchester. He also, amongst many other things, made significant and characteristically provocative contributions to the discussion "Can machines think?"

From 1945 to 1948 he was at the National Physical Laboratory, where he worked on the design of ACE (Automatic Computing Engine). In 1949 he 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 I. During this time he continued to do more abstract work, and in "Computing machinery and intelligence" (Mind, October 1950), Turing tackled 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 "sentient".

In 1952 Turing wrote a chess program. Lacking a computer powerful enough to execute it, he simulated the computer, taking about half an hour per move. One game was recorded; the program lost to a colleague of Turing.

Prosecution of Turing for his homosexuality crippled his career. In 1952, his male lover helped an accomplice to break into Turing's house and commit larceny. Turing went to the police to report the crime. As a result of the police investigation, Turing was said to have had a sexual relationship with a 19-year-old man, and Turing was charged with "gross indecency and sexual perversion". He unapologetically offered no defence, and was convicted. Following the well-publicised trial, he was given a choice between incarceration and libido-reducing hormonal treatment. He chose the estrogen hormone injections, which lasted for a year, with side effects including the development of breasts during that period. In 1954, he died of cyanide poisoning, apparently from a cyanide-laced apple he left half eaten. Most believe that his death was intentional, and the death was ruled a suicide. His mother, however, strenuously argued that the ingestion was accidental due to his careless storage of laboratory chemicals.