# Alan Turing (1912-1954)

Mathematician and founder of computer science

Alan Turing read mathematics at King’s College, Cambridge, earning a fellowship there in 1935 for a dissertation in which he rediscovered the central limit theorem of probability. Soon after, he began work on mathematical logic which took him to Princeton to work with Alonzo Church.

In 1936 he published the paper ‘On computable numbers, with an application to the Entscheidungsproblem’, introducing what has become known as the ‘universal Turing machine’ as part of a theoretical approach to a problem set a few years earlier by the mathematician David Hilbert.

With the outbreak of the Second World War, Turing became head of a codebreaking unit at Bletchley Park, home to the Government Code and Cypher School. He used his profound mathematical skill to design, with colleague Gordon Welchman, a series of huge electromechanical codebreaking machines known as ‘bombes’. These allowed the Bletchley team to crack coded messages sent by German Enigma machines – a seminal event in the history of the war. Turing also worked with more complex codes generated by Lorenz machines.

Towards the end of the war, Turing became involved with the development of secure speech encryption systems. In 1943 he spent two months at the Bell Laboratories in the USA, working with their ‘SIGSALY’ system, and on his return to the UK he moved to Hanslope Park, Buckinghamshire, developing a technology known as ‘Delilah’.

After the war Turing was recruited to the National Physical Laboratory, Teddington, where he wrote a detailed specification for a universal digital programmable computer in 1945, to be known as the ‘ACE’ or Automatic Computing Engine. He moved to Manchester University in 1948, and in his absence his plans were realised in the ‘Pilot ACE’ computer completed in 1950, now held in the collections of the Science Museum.

At Manchester, Turing continued with pioneering work in computing as well as researching the mathematics of ‘morphogenesis’ – the chemical basis of growth and pattern in living things – in his distinctive self-sufficient style.

He died by cyanide poisoning in 1954, the coroner concluding that he had committed suicide.