# Alan Turing

**Alan Turing** was an English mathematician who both created the theoretical background which described the capabilities of programmable computing devices, and also had a major practical role in the early work on them.

His 1936-37 theoretical paper *On computable numbers, with an application to the Entscheidungsproblem* is the foundation and keystone of all later theoretical work on computers; it described what is now called the Turing machine, and proved limits on what it could and could not do. This led to him spending time at the Institute for Advanced Study, where he worked with John von Neumann.

In addition to being a brilliant theoretician, Turing also had a strong practical side.

Early in World War II, he was the joint head of the team that broke into the Germans' Enigma cipher, and helped specify the 'bombe', a specialized device built by the British to find the settings used on Enigma machines. Later in the war, he visited Bell Labs, to review the SIGSALY voice-encryption system (also known as the 'X-System', or 'System X'); while there, he also spent time with Claude Shannon. On his return to the UK, he designed, and personally helped physically build (with a miniscule team of only a few people), the 'Delilah' voice-encryption system.

After the war, he moved to the National Physical Laboratory, and, perhaps inspired to some degree by von Neumann's *First Draft of a Report on the EDVAC*, Turing designed the Automatic Computing Engine, and wrote a lengthy report on it. Apparently unhappy at the delays in building it, he then moved to Manchester University, where he joined the team working on the Manchester Mark I, and wrote the first edition of the manual for it. He then became interested in artificial intelligence, and invented the Turing test.

By the early 1050's, his interests had turned to biology. On June 8, 1954 he was found dead from the ingestion of cyanide on an apple; whether deliberate (suicide) or accidental is still debated.

## Further reading

- Alan Turing,
*On computable numbers, with an application to the Entscheidungsproblem* - Sara Turing,
*Alan M. Turing*, Cambridge University, Cambridge, 1959; re-printed 2012 - Andrew Hodges,
*Alan Turing: The Enigma*, Simon & Schuster, New York, 1983 - the definitive biography - B. Jack Copeland,
*Turing: Pioneer of the Information Age*, Oxford University, Oxford, 2012 - David Leavitt,
*The Man Who Knew Too Much: Alan Turing and the Invention of the Computer*, W. W. Norton, New York, 2006 - a shorter biography; has some minor errors, but very readable - Ted Gottfried,
*Alan Turing: The Architect of the Computer Age*, Franklin Watts, 1996 - David E. Newton,
*Alan Turing: A Study in Light and Shadow*, Xlibris, 2003 - Jack Copeland, Jonathan Bowen, Mark Sprevak, Robin Wilson,
*The Turing Guide*, Oxford University, Oxford, 2017 - a large collection of essays, on a broad range of Turing-related subjects - Simon Lavington, Martin Campbell-Kelly, Chris Burton,
*Alan Turing and His Contemporaries: Building the World's First Computers*, British Informatics Society, Swindon, 2012 - ditto

## External links

- The Turing Digital Archive
- Alan Turing: The Enigma - a Web-site maintained by his biographer, Andrew Hodges
- Alan Turing - brief biography at the IEEE Computer Society