Alan Turing
Father of theoretical computer science and codebreaker who helped defeat the Nazis.
Alan Mathison Turing lived from 23 June 1912 to 7 June 1954. He was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. His work shaped theoretical computer science, especially through the Turing machine—a formal model of algorithm and computation that serves as a blueprint for a general-purpose computer. For this, he is widely regarded as the father of theoretical computer science.
Born in London, Turing grew up in southern England. He studied at King’s College, Cambridge, and earned a doctorate from Princeton University in 1938. During World War II, he worked for the Government Code and Cypher School at Bletchley Park, Britain’s codebreaking hub that produced Ultra intelligence. He led Hut 8, the unit focused on German naval codes. Turing developed methods to speed up the breaking of German ciphers, refining the pre-war Polish bomba—an electromechanical device that found Enigma machine settings. His work was vital in decrypting intercepted messages, helping the Allies defeat the Axis in the Battle of the Atlantic and other campaigns.
After the war, Turing worked at the National Physical Laboratory, where he designed the Automatic Computing Engine, an early concept for a stored-program computer. In 1948, he joined Max Newman’s Computing Machine Laboratory at the University of Manchester, helping develop early Manchester computers and turning to mathematical biology. He wrote about the chemical basis of morphogenesis and predicted oscillating chemical reactions, like the Belousov–Zhabotinsky reaction, which was first observed in the 1960s. Much of his work stayed unrecognised during his lifetime because it was classified under the Official Secrets Act.
In 1952, Turing was prosecuted for homosexual acts. He chose hormone treatment—chemical castration—rather than prison. He died on 7 June 1954, at age 41, from cyanide poisoning. An inquest ruled it suicide, though the evidence also allows for accidental poisoning. After a 2009 campaign, British Prime Minister Gordon Brown issued an official apology for “the appalling way [Turing] was treated.” Queen Elizabeth II granted a pardon in 2013. The informal term “Alan Turing law” refers to a 2017 UK law that retroactively pardoned men cautioned or convicted under historical anti-homosexuality legislation.
Turing’s legacy in mathematics and computing is widely recognised through statues and numerous namesakes, including an annual award for computing innovation. His portrait appears on the Bank of England £50 note, first released on 23 June 2021, his birthday. In a 2019 BBC series, the audience voted him the greatest scientist of the 20th century.
Cognitive scientist Douglas Hofstadter wrote: “Atheist, homosexual, eccentric, marathon-running mathematician, A. M. Turing was in large part responsible not only for the concept of computers, incisive theorems about their powers, and a clear vision of the possibility of computer minds, but also for the cracking of German ciphers during the Second World War. It is fair to say we owe much to Alan Turing for the fact that we are not under Nazi rule today.”
Turing was born in Maida Vale, London, while his father, Julius Mathison Turing, was on leave from the Indian Civil Service in Chatrapur, then in the Madras Presidency (now Odisha, India). Julius was the son of a clergyman, Rev. John Robert Turing, from a Scottish merchant family based in the Netherlands that included a baronet. Turing’s mother, Ethel Sara Turing (née Stoney), was the daughter of Edward Waller Stoney, chief engineer of the Madras Railways. The Stoneys were a Protestant Anglo-Irish gentry family from County Tipperary and County Longford; Ethel spent much of her childhood in County Clare. Julius and Ethel married on 1 October 1907 at St. Bartholomew’s Church in Ballsbridge, Dublin.
Julius’s work with the ICS brought the family to British India, where his grandfather had been a general in the Bengal Army. But Julius and Ethel wanted their children raised in Britain, so they moved to Maida Vale, London, where Alan was born on 23 June 1912. A blue plaque marks the nursing home, later the Colonnade Hotel. Turing had an older brother, John Ferrier Turing, father of Dermot Turing, 12th Baronet of the Turing baronets. In 1922, Turing read *Natural Wonders Every Child Should Know* by Edwin Tenney Brewster, which he credited with sparking his interest in science.
During Turing’s childhood, his father’s civil service commission remained active, so his parents travelled between Hastings, UK, and India, leaving the two sons with a retired Army couple. In Hastings, Turing stayed at Baston Lodge, Upper Maze Hill, St Leonards-on-Sea, now marked with a blue plaque unveiled on 23 June 2012, the centenary of his birth. In 1927, his parents bought a house in Guildford, where Turing lived during school holidays; that location also has a blue plaque.
Turing attended St Michael’s, a primary school at 20 Charles Road, St Leonards-on-Sea, from age six to nine. The headmistress recognised his abilities early on.
- born
- 23 June 1912, Maida Vale, London
- died
- 7 June 1954, aged 41, from cyanide poisoning
- field
- Mathematics, computer science, logic, cryptanalysis, philosophy, theoretical biology
- nationality
- English
- known_for
- Turing machine, cracking German ciphers during World War II, Automatic Computing Engine, chemical basis of morphogenesis
Lore & Background
Born in London, Turing was raised in southern England. He graduated from King's College, Cambridge, and in 1938, earned a doctorate degree from Princeton University. During World War II, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence. He led Hut 8, the section responsible for German naval cryptanalysis. Turing devised techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bomba method, an electromechanical machine that could find settings for the Enigma machine. He played a crucial role in cracking intercepted messages that enabled the Allies to defeat the Axis powers in the Battle of the Atlantic and other engagements. After the war, Turing worked at the National Physical Laboratory, where he designed the Automatic Computing Engine, one of the first designs for a stored-program computer. In 1948, Turing joined Max Newman's Computing Machine Laboratory at the University of Manchester, where he contributed to the development of early Manchester computers and became interested in mathematical biology. Turing wrote on the chemical basis of morphogenesis and predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s. Despite these accomplishments, he was never fully recognised during his lifetime because much of his work was covered by the Official Secrets Act. In 1952, Turing was prosecuted for homosexual acts. He accepted hormone treatment, a procedure commonly referred to as chemical castration, as an alternative to prison. Turing died on 7 June 1954, aged 41, from cyanide poisoning. An inquest determined his death as suicide, but the evidence is also consistent with accidental poisoning. Following a campaign in 2009, British prime minister Gordon Brown made an official public apology for 'the appalling way [Turing] was treated'. Queen Elizabeth II granted a pardon in 2013. The term 'Alan Turing law' is used informally to refer to a 2017 law in the UK that retroactively pardoned men cautioned or convicted under historical legislation that outlawed homosexual acts.
Reader's Guide
Turing left an extensive legacy in mathematics and computing which has become widely recognised with statues and many things named after him, including an annual award for computing innovation. His portrait appears on the Bank of England £50 note, first released on 23 June 2021 to coincide with his birthday. The audience vote in a 2019 BBC series named Turing the greatest scientist of the 20th century. This recognition stems from his foundational role in theoretical computer science, where he formalised the concepts of algorithm and computation through the Turing machine, a model of a general-purpose computer. During World War II, he led Hut 8 at Bletchley Park, devising techniques to speed the breaking of German ciphers, including improvements to the Polish bomba method, and played a crucial role in cracking intercepted messages that helped the Allies defeat the Axis in the Battle of the Atlantic. After the war, he designed the Automatic Computing Engine, an early stored-program computer, and later contributed to early Manchester computers while turning to mathematical biology, writing on the chemical basis of morphogenesis and predicting oscillating chemical reactions later observed in the 1960s. Much of his work remained unrecognised during his lifetime due to the Official Secrets Act. In 1952, he was prosecuted for homosexual acts and accepted chemical castration as an alternative to prison. He died from cyanide poisoning in 1954, with an inquest ruling suicide, though accidental poisoning is also consistent with the evidence. A 2009 campaign led to an official apology from the British prime minister, and Queen Elizabeth II granted a pardon in 2013. The cognitive scientist Douglas Hofstadter summarised Turing’s impact by noting his contributions to computer concepts, theorems about computer powers, the vision of computer minds, and the cracking of German ciphers, concluding that we owe much to him for not being under Nazi rule.
Did You Know?
- Turing was born in Maida Vale, London, on 23 June 1912.
- He died on 7 June 1954, aged 41, from cyanide poisoning.
- He led Hut 8 at Bletchley Park, responsible for German naval cryptanalysis.
- Turing designed the Automatic Computing Engine, one of the first designs for a stored-program computer.
- He predicted oscillating chemical reactions such as the Belousov–Zhabotinsky reaction, first observed in the 1960s.
Notable Quotes (Wikiquote)
"A man provided with paper, pencil, and rubber, and subject to strict discipline, is in effect a universal machine." — Alan Turing "Intelligent Machinery." This passage was one of the epigraphs to Cryptonomicon, the influential novel by Neal Stephenson, in which Turing was a fictionalized character. It shared a page with a quote from Imelda Marcos." — Alan Turing "'The Mechanical Brain. Answer Found to 300 Year Old Problem' The Times newspaper, 11 June 1949 page 4 column 5." — Alan Turing "The sentence in bold appears on the latest British £50 bank note featuring Alan Turing which was released on 23 June 2021 on what would have been his 109th birthday." — Alan Turing
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