# Alan Turing "Turing" redirects here. For other uses, see [Turing (disambiguation)](https://en.wikipedia.org/wiki/Turing_\(disambiguation\) "Turing (disambiguation)"). Alan Turing [OBE](https://en.wikipedia.org/wiki/Officer_of_the_Order_of_the_British_Empire "Officer of the Order of the British Empire") [FRS](https://en.wikipedia.org/wiki/Fellow_of_the_Royal_Society "Fellow of the Royal Society") [![](https://upload.wikimedia.org/wikipedia/commons/thumb/c/ce/Alan_turing_header.jpg/250px-Alan_turing_header.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_turing_header.jpg) Turing in 1951 Born Alan Mathison Turing (1912-06-23)23 June 1912 [Maida Vale](https://en.wikipedia.org/wiki/Maida_Vale "Maida Vale"), London, England Died 7 June 1954(1954-06-07) (aged 41) [Wilmslow](https://en.wikipedia.org/wiki/Wilmslow "Wilmslow"), Cheshire, England Cause of death Suicide by [cyanide poisoning](https://en.wikipedia.org/wiki/Cyanide_poisoning "Cyanide poisoning") Education - [University of Cambridge](https://en.wikipedia.org/wiki/University_of_Cambridge "University of Cambridge") ([MA](https://en.wikipedia.org/wiki/Master_of_Arts_\(Oxford,_Cambridge,_and_Dublin\) "Master of Arts (Oxford, Cambridge, and Dublin)")) - [Princeton University](https://en.wikipedia.org/wiki/Princeton_University "Princeton University") (PhD) Known for - [Cryptanalysis of the Enigma](https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma "Cryptanalysis of the Enigma") - [Turing's proof](https://en.wikipedia.org/wiki/Turing's_proof "Turing's proof") - [Turing machine](https://en.wikipedia.org/wiki/Turing_machine "Turing machine") - [Turing test](https://en.wikipedia.org/wiki/Turing_test "Turing test") - [unorganised machine](https://en.wikipedia.org/wiki/Unorganized_machine "Unorganized machine") - [Turing pattern](https://en.wikipedia.org/wiki/Turing_pattern "Turing pattern") - [Turing reduction](https://en.wikipedia.org/wiki/Turing_reduction "Turing reduction") - "[The Chemical Basis of Morphogenesis](https://en.wikipedia.org/wiki/The_Chemical_Basis_of_Morphogenesis "The Chemical Basis of Morphogenesis")" - [Turing paradox](https://en.wikipedia.org/wiki/Quantum_Zeno_effect "Quantum Zeno effect") Awards [Smith's Prize](https://en.wikipedia.org/wiki/Smith's_Prize "Smith's Prize") (1936) **Scientific career** Fields - [Logic](https://en.wikipedia.org/wiki/Logic "Logic") - mathematics - [cryptanalysis](https://en.wikipedia.org/wiki/Cryptanalysis "Cryptanalysis") - [computer science](https://en.wikipedia.org/wiki/Computer_science "Computer science") - [mathematical and theoretical biology](https://en.wikipedia.org/wiki/Mathematical_and_theoretical_biology "Mathematical and theoretical biology") Institutions - [University of Manchester](https://en.wikipedia.org/wiki/University_of_Manchester "University of Manchester") - [Government Code and Cypher School](https://en.wikipedia.org/wiki/Government_Code_and_Cypher_School "Government Code and Cypher School") - [National Physical Laboratory](https://en.wikipedia.org/wiki/National_Physical_Laboratory_\(United_Kingdom\) "National Physical Laboratory (United Kingdom)") [Thesis](https://en.wikipedia.org/wiki/Thesis "Thesis") _[Systems of Logic Based on Ordinals](https://web.archive.org/web/20121023103503/https://webspace.princeton.edu/users/jedwards/Turing%20Centennial%202012/Mudd%20Archive%20files/12285_AC100_Turing_1938.pdf)_ (1938) [Doctoral advisor](https://en.wikipedia.org/wiki/Doctoral_advisor "Doctoral advisor") [Alonzo Church](https://en.wikipedia.org/wiki/Alonzo_Church "Alonzo Church") Doctoral students - [Robin Gandy](https://en.wikipedia.org/wiki/Robin_Gandy "Robin Gandy") - [Beatrice Worsley](https://en.wikipedia.org/wiki/Beatrice_Worsley "Beatrice Worsley") Signature [![](https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Alan_Turing_signature.svg/250px-Alan_Turing_signature.svg.png?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_signature.svg) **Alan Mathison Turing** ([/ˈtjʊərɪŋ/](https://en.wikipedia.org/wiki/Help:IPA/English "Help:IPA/English"); 23 June 1912 – 7 June 1954) was an English mathematician, [computer scientist](https://en.wikipedia.org/wiki/Computer_scientist "Computer scientist"), [logician](https://en.wikipedia.org/wiki/Logic "Logic"), [cryptanalyst](https://en.wikipedia.org/wiki/Cryptanalyst "Cryptanalyst"), philosopher and [theoretical biologist](https://en.wikipedia.org/wiki/Theoretical_biologist "Theoretical biologist"). He was highly influential in the development of [theoretical computer science](https://en.wikipedia.org/wiki/Theoretical_computer_science "Theoretical computer science"), providing a formalisation of the concepts of [algorithm](https://en.wikipedia.org/wiki/Algorithm "Algorithm") and [computation](https://en.wikipedia.org/wiki/Computation "Computation") with the [Turing machine](https://en.wikipedia.org/wiki/Turing_machine "Turing machine"), which can be considered a model of a general-purpose computer. Turing is widely considered to be the father of theoretical computer science. Born in London, Turing was raised in [southern England](https://en.wikipedia.org/wiki/Southern_England "Southern England"). He graduated from [King's College, Cambridge](https://en.wikipedia.org/wiki/University_of_Cambridge "University of Cambridge"), and in 1938, earned a doctorate degree from [Princeton University](https://en.wikipedia.org/wiki/Princeton_University "Princeton University"). During [World War II](https://en.wikipedia.org/wiki/World_War_II "World War II"), Turing worked for the [Government Code and Cypher School](https://en.wikipedia.org/wiki/Government_Code_and_Cypher_School "Government Code and Cypher School") at [Bletchley Park](https://en.wikipedia.org/wiki/Bletchley_Park "Bletchley Park"), Britain's [codebreaking](https://en.wikipedia.org/wiki/Codebreaking "Codebreaking") centre that produced [Ultra](https://en.wikipedia.org/wiki/Ultra_\(cryptography\) "Ultra (cryptography)") intelligence. He led [Hut 8](https://en.wikipedia.org/wiki/Hut_8 "Hut 8"), the section responsible for German naval cryptanalysis. Turing devised techniques for speeding the breaking of German [ciphers](https://en.wikipedia.org/wiki/Cipher "Cipher"), including improvements to the pre-war Polish [bomba](https://en.wikipedia.org/wiki/Bomba_\(cryptography\) "Bomba (cryptography)") method, an [electromechanical](https://en.wikipedia.org/wiki/Electromechanical "Electromechanical") machine that could find settings for the [Enigma machine](https://en.wikipedia.org/wiki/Enigma_machine "Enigma machine"). He played a crucial role in cracking intercepted messages that enabled the [Allies](https://en.wikipedia.org/wiki/Allies_of_World_War_2 "Allies of World War 2") to defeat the [Axis powers](https://en.wikipedia.org/wiki/Axis_powers "Axis powers") in the [Battle of the Atlantic](https://en.wikipedia.org/wiki/Battle_of_the_Atlantic "Battle of the Atlantic") and other engagements. After the war, Turing worked at the [National Physical Laboratory](https://en.wikipedia.org/wiki/National_Physical_Laboratory_\(United_Kingdom\) "National Physical Laboratory (United Kingdom)"), where he designed the [Automatic Computing Engine](https://en.wikipedia.org/wiki/Automatic_Computing_Engine "Automatic Computing Engine"), one of the first designs for a stored-program computer. In 1948, Turing joined [Max Newman](https://en.wikipedia.org/wiki/Max_Newman "Max Newman")'s [Computing Machine Laboratory](https://en.wikipedia.org/wiki/Computing_Machine_Laboratory "Computing Machine Laboratory") at the [University of Manchester](https://en.wikipedia.org/wiki/University_of_Manchester "University of Manchester"), where he contributed to the development of early [Manchester computers](https://en.wikipedia.org/wiki/Manchester_computers "Manchester computers") and became interested in [mathematical biology](https://en.wikipedia.org/wiki/Mathematical_biology "Mathematical biology"). Turing wrote on the chemical basis of [morphogenesis](https://en.wikipedia.org/wiki/Morphogenesis "Morphogenesis") and predicted [oscillating chemical reactions](https://en.wikipedia.org/wiki/Chemical_oscillator "Chemical oscillator") such as the [Belousov–Zhabotinsky reaction](https://en.wikipedia.org/wiki/Belousov%E2%80%93Zhabotinsky_reaction "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](https://en.wikipedia.org/wiki/Official_Secrets_Act_1939 "Official Secrets Act 1939"). In 1952, Turing was prosecuted for [homosexual acts](https://en.wikipedia.org/wiki/Gross_indecency "Gross indecency"). He accepted hormone treatment, a procedure commonly referred to as [chemical castration](https://en.wikipedia.org/wiki/Chemical_castration "Chemical castration"), as an alternative to prison. Turing died on 7 June 1954, aged 41, from [cyanide poisoning](https://en.wikipedia.org/wiki/Cyanide_poisoning "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](https://en.wikipedia.org/wiki/Gordon_Brown "Gordon Brown") made an [official public apology](https://en.wikipedia.org/wiki/Alan_Turing#Government_apology_and_pardon) for "the appalling way \[Turing\] was treated". [Queen Elizabeth II](https://en.wikipedia.org/wiki/Queen_Elizabeth_II "Queen Elizabeth II") granted a [pardon](https://en.wikipedia.org/wiki/Royal_prerogative_of_mercy "Royal prerogative of mercy") in 2013. The term "[Alan Turing law](https://en.wikipedia.org/wiki/Alan_Turing_law "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. Turing left [an extensive legacy](https://en.wikipedia.org/wiki/Legacy_of_Alan_Turing "Legacy of Alan Turing") in mathematics and computing which has become widely recognised with statues and [many things named after him](https://en.wikipedia.org/wiki/List_of_things_named_after_Alan_Turing "List of things named after Alan Turing"), including [an annual award](https://en.wikipedia.org/wiki/Turing_Award "Turing Award") for computing innovation. His portrait appears on the [Bank of England £50 note](https://en.wikipedia.org/wiki/Bank_of_England_%C2%A350_note "Bank of England £50 note"), first released on 23 June 2021 to coincide with his birthday. The audience vote in a [2019 BBC series](https://en.wikipedia.org/wiki/Icons:_The_Greatest_Person_of_the_20th_Century "Icons: The Greatest Person of the 20th Century") named Turing the greatest scientist of the 20th century. The cognitive scientist [Douglas Hofstadter](https://en.wikipedia.org/wiki/Douglas_Hofstadter "Douglas Hofstadter") writes: > 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." ## Early life and education ### Family [![](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Alan_Turing_%285025990183%29.jpg/250px-Alan_Turing_%285025990183%29.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_\(5025990183\).jpg) [English Heritage](https://en.wikipedia.org/wiki/English_Heritage "English Heritage") [blue plaque](https://en.wikipedia.org/wiki/Blue_plaque "Blue plaque") in [Maida Vale](https://en.wikipedia.org/wiki/Maida_Vale "Maida Vale"), London, marking Turing's birthplace in 1912 Turing was born in [Maida Vale](https://en.wikipedia.org/wiki/Maida_Vale "Maida Vale"), London, while his father, Julius Mathison Turing, was on leave from his position with the [Indian Civil Service](https://en.wikipedia.org/wiki/Indian_Civil_Service "Indian Civil Service") (ICS) of the [British Raj government](https://en.wikipedia.org/wiki/British_Raj "British Raj") at [Chatrapur](https://en.wikipedia.org/wiki/Chatrapur "Chatrapur"), then in the [Madras Presidency](https://en.wikipedia.org/wiki/Madras_Presidency "Madras Presidency") and presently in [Odisha](https://en.wikipedia.org/wiki/Odisha "Odisha") state, in India. Turing's father was the son of a clergyman, the Rev. John Robert Turing, from a Scottish family of merchants that had been based in the Netherlands and included a [baronet](https://en.wikipedia.org/wiki/Baronet "Baronet"). Turing's mother, Julius's wife, was Ethel Sara Turing (née Stoney), daughter of [Edward Waller Stoney](https://en.wikipedia.org/wiki/Edward_Waller_Stoney "Edward Waller Stoney"), chief engineer of the [Madras Railways](https://en.wikipedia.org/wiki/Madras_and_Southern_Mahratta_Railway "Madras and Southern Mahratta Railway"). The Stoneys were a [Protestant](https://en.wikipedia.org/wiki/Protestantism_in_Ireland "Protestantism in Ireland") [Anglo-Irish](https://en.wikipedia.org/wiki/Anglo-Irish_people "Anglo-Irish people") [gentry](https://en.wikipedia.org/wiki/Gentry "Gentry") family from both [County Tipperary](https://en.wikipedia.org/wiki/County_Tipperary "County Tipperary") and [County Longford](https://en.wikipedia.org/wiki/County_Longford "County Longford"), while Ethel herself had spent much of her childhood in [County Clare](https://en.wikipedia.org/wiki/County_Clare "County Clare"). Julius and Ethel married on 1 October 1907 at the Church of Ireland [St. Bartholomew's Church](https://en.wikipedia.org/wiki/St_Bartholomew's_Church,_Dublin "St Bartholomew's Church, Dublin") on [Clyde Road](https://en.wikipedia.org/wiki/Clyde_Road "Clyde Road") in [Ballsbridge](https://en.wikipedia.org/wiki/Ballsbridge "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](https://en.wikipedia.org/wiki/Bengal_Army "Bengal Army"). However, both Julius and Ethel wanted their children to be brought up in Britain, so they moved to [Maida Vale](https://en.wikipedia.org/wiki/Maida_Vale "Maida Vale"), London, where Alan Turing was born on 23 June 1912, as recorded by a [blue plaque](https://en.wikipedia.org/wiki/Blue_plaque "Blue plaque") on the outside of the nursing home where he was born, which later became the [Colonnade Hotel](https://en.wikipedia.org/wiki/Colonnade_Hotel_\(London\) "Colonnade Hotel (London)"). Turing had an elder brother, John Ferrier Turing, father of [Dermot Turing](https://en.wikipedia.org/wiki/Dermot_Turing "Dermot Turing"), 12th Baronet of the [Turing baronets](https://en.wikipedia.org/wiki/Turing_baronets "Turing baronets"). In 1922, he discovered _Natural Wonders Every Child Should Know_ by [Edwin Tenney Brewster](https://en.wikipedia.org/wiki/Edwin_Tenney_Brewster "Edwin Tenney Brewster"). He credited it with opening his eyes to science. Turing's father's civil service commission was still active during Turing's childhood years, and his parents travelled between [Hastings](https://en.wikipedia.org/wiki/Hastings "Hastings") in the United Kingdom and India, leaving their two sons to stay with a retired [Army](https://en.wikipedia.org/wiki/British_Army "British Army") couple. At Hastings, Turing stayed at [Baston Lodge](https://en.wikipedia.org/wiki/Baston_Lodge "Baston Lodge"), Upper Maze Hill, [St Leonards-on-Sea](https://en.wikipedia.org/wiki/St_Leonards-on-Sea "St Leonards-on-Sea"), now marked with a blue plaque. The plaque was unveiled on 23 June 2012, the centenary of Turing's birth. Very early in life, Turing's parents purchased a house in [Guildford](https://en.wikipedia.org/wiki/Guildford "Guildford") in 1927, and Turing lived there during school holidays. The location is also marked with a blue plaque. ### School [![](https://upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Alan_Turing_Aged_16.jpg/250px-Alan_Turing_Aged_16.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_Aged_16.jpg) Turing at age 16, c. 1928 – c. 1929 Turing's parents enrolled him at St Michael's, a primary school at 20 Charles Road, [St Leonards-on-Sea](https://en.wikipedia.org/wiki/St_Leonards-on-Sea "St Leonards-on-Sea"), from the age of six to nine. The headmistress recognised his talent, noting that she "...had clever boys and hardworking boys, but Alan is a genius". Between January 1922 and 1926, Turing was educated at Hazelhurst Preparatory School, an independent school in the village of [Frant](https://en.wikipedia.org/wiki/Frant "Frant") in Sussex (now [East Sussex](https://en.wikipedia.org/wiki/East_Sussex "East Sussex")). In 1926, at the age of 13, he went on to [Sherborne School](https://en.wikipedia.org/wiki/Sherborne_School "Sherborne School"), an independent boarding school in the market town of [Sherborne](https://en.wikipedia.org/wiki/Sherborne "Sherborne") in Dorset, where he boarded at Westcott House. The first day of term coincided with the [1926 General Strike](https://en.wikipedia.org/wiki/1926_United_Kingdom_general_strike "1926 United Kingdom general strike"), in Britain, but Turing was so determined to attend that he rode his bicycle unaccompanied 60 miles (97 km) from [Southampton](https://en.wikipedia.org/wiki/Southampton "Southampton") to Sherborne, stopping overnight at an inn. Turing's natural inclination towards mathematics and science did not earn him respect from some of the teachers at Sherborne, whose [definition of education](https://en.wikipedia.org/wiki/Definition_of_education "Definition of education") placed more emphasis on the [classics](https://en.wikipedia.org/wiki/Classics "Classics"). His headmaster wrote to his parents: "I hope he will not fall between two stools. If he is to stay at public school, he must aim at becoming _educated_. If he is to be solely a _Scientific Specialist_, he is wasting his time at a public school". Despite this, Turing continued to show remarkable ability in the studies he loved, solving advanced problems in 1927 without having studied even elementary [calculus](https://en.wikipedia.org/wiki/Calculus "Calculus"). In 1928, aged 16, Turing encountered [Albert Einstein](https://en.wikipedia.org/wiki/Albert_Einstein "Albert Einstein")'s work; not only did he grasp it, but it is possible that he managed to deduce Einstein's questioning of [Newton's laws of motion](https://en.wikipedia.org/wiki/Newton's_laws_of_motion "Newton's laws of motion") from a text in which this was never made explicit. [![](https://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Alan_Turing_in_Cornwall_April_1930_with_Peter_Hogg%2C_Edwin_Davis%2C_John_Bennett%2C_Peter_White%2C_and_Duncan_Carse.jpg/330px-Alan_Turing_in_Cornwall_April_1930_with_Peter_Hogg%2C_Edwin_Davis%2C_John_Bennett%2C_Peter_White%2C_and_Duncan_Carse.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_in_Cornwall_April_1930_with_Peter_Hogg,_Edwin_Davis,_John_Bennett,_Peter_White,_and_Duncan_Carse.jpg) Turing (seated second from left) in [Cornwall](https://en.wikipedia.org/wiki/Cornwall "Cornwall"), with fellow Shirburnians: Edwin Davis, John Bennett, Peter White, [Peter Hogg](https://en.wikipedia.org/wiki/Peter_Hogg_\(Shiburnian\) "Peter Hogg (Shiburnian)") (seated second from right), and Duncan Carse, in April 1930. ### Christopher Morcom Main article: [Christopher Morcom](https://en.wikipedia.org/wiki/Christopher_Morcom "Christopher Morcom") At Sherborne, Turing formed a significant friendship with fellow pupil Christopher Collan Morcom (13 July 1911 – 13 February 1930), who has been described as Turing's first love. Morcom was a student athlete, photographer, music collector, and astronomer, notable for [his elaborate school pranks](https://en.wikipedia.org/wiki/Christopher_Morcom#Sense_of_humour "Christopher Morcom"). Their relationship, particularly in discussion of science and astronomy, is collected in letters. _The Enigma_ details how Morcom "used to tease Alan a good deal", with various running [in-jokes](https://en.wikipedia.org/wiki/In-joke "In-joke") and pranks to inconvenience Turing. Nevertheless, their intellectual correspondences provided inspiration in Turing's future endeavours. In February 1930, shortly before graduation, their relationship was cut short by Morcom's death. Months prior, the two had had a weeklong tour of [Trinity College, Cambridge](https://en.wikipedia.org/wiki/Trinity_College,_Cambridge "Trinity College, Cambridge") to sit [scholarship](https://en.wikipedia.org/wiki/Scholarship "Scholarship") examinations. Days after attending a [Salisbury Singers](https://en.wikipedia.org/wiki/Salisbury_Singers "Salisbury Singers") concert, Morcom died of complications of [bovine tuberculosis](https://en.wikipedia.org/wiki/Bovine_tuberculosis "Bovine tuberculosis"), which he had contracted earlier in life. Morcom's death caused Turing great sorrow. He accepted multiple prizes on Morcom's behalf, choosing books in Morcom's memory as prizes; and Turing also won the posthumous Christopher Morcom Science Prize, organized by Morcom's mother. In a letter to Morcom's mother, Frances Isobel Morcom (née Swan), Turing wrote: > I am sure I could not have found anywhere another companion so brilliant and yet so charming and unconceited. I regarded my interest in my work, and in such things as astronomy (to which he introduced me) as something to be shared with him and I think he felt a little the same about me ... I know I must put as much energy if not as much interest into my work as if he were alive, because that is what he would like me to do. Turing's relationship with Morcom's mother continued long after Morcom's death, with her sending gifts to Turing, and him sending letters, typically on Morcom's birthday. A day before the third anniversary of Morcom's death (13 February 1933), he wrote to Mrs. Morcom: > I expect you will be thinking of Chris when this reaches you. I shall too, and this letter is just to tell you that I shall be thinking of Chris and of you tomorrow. I am sure that he is as happy now as he was when he was here. Your affectionate Alan. It has been speculated that Morcom's death was the cause of Turing's [atheism](https://en.wikipedia.org/wiki/Atheism "Atheism") and "the conviction that all phenomena must have [materialistic](https://en.wikipedia.org/wiki/Materialism "Materialism") explanations". Circa 1932, Turing wrote _The Nature of Spirit_ while visiting Morcom's family home. His writings show a belief in such concepts as a spirit surviving death independent of the body. In a later letter, also written to Morcom's mother, Turing wrote: > Personally, I believe that spirit is really eternally connected with matter but certainly not by the same kind of body ... as regards the actual connection between spirit and body I consider that the body can hold on to a 'spirit', whilst the body is alive and awake the two are firmly connected. When the body is asleep I cannot guess what happens but when the body dies, the 'mechanism' of the body, holding the spirit is gone and the spirit finds a new body sooner or later, perhaps immediately. ### University and work on computability [![](https://upload.wikimedia.org/wikipedia/commons/thumb/7/79/Alan_Turing_az_1930-as_%C3%A9vekben.jpg/250px-Alan_Turing_az_1930-as_%C3%A9vekben.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_az_1930-as_%C3%A9vekben.jpg) Turing in the 1930s In 1929 Turing and his friend [Christopher Morcom](https://en.wikipedia.org/wiki/Christopher_Morcom "Christopher Morcom") applied for scholarships at [Trinity College, Cambridge](https://en.wikipedia.org/wiki/Trinity_College,_Cambridge "Trinity College, Cambridge"). Morcom, who was successful, had various advantages over Turing – he was nearly a year older, and both his father and brother had studied at Trinity. However, he died three months after the offer was made. Turing, on the other hand, was unsuccessful, but sat the [King's College, Cambridge](https://en.wikipedia.org/wiki/King's_College,_Cambridge "King's College, Cambridge") Scholarship Examination in Mathematics in 1930. King's reserved most of its places for [Etonians](https://en.wikipedia.org/wiki/Etonians "Etonians") (there was a historic link with Eton as a feeder institution), making the exam very competitive for candidates from other schools. However, its examiners had a slightly different slant to those in other colleges. Hodges describes the King's examiners as looking for "a spark of originality" and notes that the papers were "notorious for their unorthodox questions". Turing was awarded an [exhibition](https://en.wikipedia.org/wiki/Exhibition_\(scholarship\) "Exhibition (scholarship)") (a lower-value scholarship) worth £80 per annum (equivalent to about £4,300 as of 2023). His undergraduate studies at Cambridge were from February 1931 to November 1934. He studied "Schedule B" of the [Mathematical Tripos](https://en.wikipedia.org/wiki/Mathematical_Tripos "Mathematical Tripos") course. He was awarded first-class honours in mathematics. His dissertation, _On the Gaussian error function_, written during his senior year and delivered in November 1934 proved a version of the [central limit theorem](https://en.wikipedia.org/wiki/Central_limit_theorem "Central limit theorem"). It was finally accepted on 16 March 1935. By spring of that same year, Turing started his master's course ([Part III](https://en.wikipedia.org/wiki/Part_III_of_the_Mathematical_Tripos "Part III of the Mathematical Tripos"))—which he completed in 1937—and, at the same time, he published his first paper, a one-page article called _Equivalence of left and right almost periodicity_ (sent on 23 April), featured in the tenth volume of the _[Journal of the London Mathematical Society](https://en.wikipedia.org/wiki/London_Mathematical_Society "London Mathematical Society")_. Later that year, Turing was elected a [Fellow](https://en.wikipedia.org/wiki/Fellow "Fellow") of King's College on the strength of his dissertation where he served as a lecturer. However, unknown to Turing, the version of the theorem he proved in his paper had already been proven by [Jarl Waldemar Lindeberg](https://en.wikipedia.org/wiki/Jarl_Waldemar_Lindeberg "Jarl Waldemar Lindeberg") in 1922. Despite this, the committee found Turing's methods original and so regarded the work worthy of consideration for the fellowship. [Abram Besicovitch](https://en.wikipedia.org/wiki/Abram_Besicovitch "Abram Besicovitch")'s report for the committee went so far as to say that if Turing's work had been published before Lindeberg's, it would have been "an important event in the mathematical literature of that year". Between the springs of 1935 and 1936, at the same time as [Alonzo Church](https://en.wikipedia.org/wiki/Alonzo_Church "Alonzo Church"), Turing worked on the decidability of problems, starting from [Gödel's incompleteness theorems](https://en.wikipedia.org/wiki/G%C3%B6del's_incompleteness_theorems "Gödel's incompleteness theorems"). In mid-April 1936, Turing sent Max Newman the first draft typescript of his investigations. That same month, Church published his _An Unsolvable Problem of Elementary Number Theory_, with similar conclusions to Turing's then-yet unpublished work. Finally, on 28 May of that year, he finished and delivered his 36-page paper for publication called "[On Computable Numbers, with an Application to the Entscheidungsproblem](https://en.wikipedia.org/wiki/On_Computable_Numbers,_with_an_Application_to_the_Entscheidungsproblem "On Computable Numbers, with an Application to the Entscheidungsproblem")". It was published in the _Proceedings of the London Mathematical Society_ journal in two parts, the first on 30 November and the second on 23 December. In this paper, Turing reformulated [Kurt Gödel](https://en.wikipedia.org/wiki/Kurt_G%C3%B6del "Kurt Gödel")'s 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as [Turing machines](https://en.wikipedia.org/wiki/Turing_machine "Turing machine"). The _[Entscheidungsproblem](https://en.wikipedia.org/wiki/Entscheidungsproblem "Entscheidungsproblem")_ (decision problem) was originally posed by German mathematician [David Hilbert](https://en.wikipedia.org/wiki/David_Hilbert "David Hilbert") in 1928. Turing proved that his "universal computing machine" would be capable of performing any conceivable mathematical computation if it were representable as an [algorithm](https://en.wikipedia.org/wiki/Algorithm "Algorithm"). He went on to prove that there was no solution to the _decision problem_ by first showing that the [halting problem](https://en.wikipedia.org/wiki/Halting_problem "Halting problem") for Turing machines is [undecidable](https://en.wikipedia.org/wiki/Decision_problem "Decision problem"): it is not possible to decide algorithmically whether a Turing machine will ever halt. This paper has been called "easily the most influential math paper in history". [![](https://upload.wikimedia.org/wikipedia/commons/thumb/4/46/20130808_Kings_College_Front_Court_Fountain_Crop_03.jpg/250px-20130808_Kings_College_Front_Court_Fountain_Crop_03.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:20130808_Kings_College_Front_Court_Fountain_Crop_03.jpg) [King's College, Cambridge](https://en.wikipedia.org/wiki/King's_College,_Cambridge "King's College, Cambridge"), where Turing was an undergraduate in 1931 and became a Fellow in 1935. The computer room is named after him. Although [Turing's proof](https://en.wikipedia.org/wiki/Turing's_proof "Turing's proof") was published shortly after Church's equivalent proof using his [lambda calculus](https://en.wikipedia.org/wiki/Lambda_calculus "Lambda calculus"), Turing's approach is considerably more accessible and intuitive than Church's. It also included a notion of a 'Universal Machine' (now known as a [universal Turing machine](https://en.wikipedia.org/wiki/Universal_Turing_machine "Universal Turing machine")), with the idea that such a machine could perform the tasks of any other computation machine (as indeed could Church's lambda calculus). According to the [Church–Turing thesis](https://en.wikipedia.org/wiki/Church%E2%80%93Turing_thesis "Church–Turing thesis"), Turing machines and the lambda calculus are capable of computing anything that is computable. [John von Neumann](https://en.wikipedia.org/wiki/John_von_Neumann "John von Neumann") acknowledged that the central concept of the modern computer was due to Turing's paper. To this day, Turing machines are a central object of study in [theory of computation](https://en.wikipedia.org/wiki/Theory_of_computation "Theory of computation"). From September 1936 to July 1938, Turing spent most of his time studying under Church at [Princeton University](https://en.wikipedia.org/wiki/Princeton_University "Princeton University"), in the second year as a [Jane Eliza Procter Visiting Fellow](https://en.wikipedia.org/wiki/Jane_Eliza_Procter_Fellowship "Jane Eliza Procter Fellowship"). In addition to his purely mathematical work, he studied cryptology and also built three of four stages of an electro-mechanical [binary multiplier](https://en.wikipedia.org/wiki/Binary_multiplier "Binary multiplier"). In June 1938, he obtained his PhD from the [Department of Mathematics](https://en.wikipedia.org/wiki/Princeton_University_Department_of_Mathematics "Princeton University Department of Mathematics") at Princeton; his dissertation, _[Systems of Logic Based on Ordinals](https://en.wikipedia.org/wiki/Systems_of_Logic_Based_on_Ordinals "Systems of Logic Based on Ordinals")_, introduced the concept of [ordinal logic](https://en.wikipedia.org/wiki/Ordinal_logic "Ordinal logic") and the notion of [relative computing](https://en.wikipedia.org/wiki/Turing_reduction "Turing reduction"), in which Turing machines are augmented with so-called [oracles](https://en.wikipedia.org/wiki/Oracle_machine "Oracle machine"), allowing the study of problems that cannot be solved by Turing machines. Von Neumann wanted to hire him as his [postdoctoral assistant](https://en.wikipedia.org/wiki/Postdoctoral_researcher "Postdoctoral researcher"), but he went back to the United Kingdom. ## Career and research When Turing returned to Cambridge, he attended lectures given in 1939 by [Ludwig Wittgenstein](https://en.wikipedia.org/wiki/Ludwig_Wittgenstein "Ludwig Wittgenstein") about the [foundations of mathematics](https://en.wikipedia.org/wiki/Foundations_of_mathematics "Foundations of mathematics"). The lectures have been reconstructed verbatim, including interjections from Turing and other students, from students' notes. Turing and Wittgenstein argued and disagreed, with Turing defending [formalism](https://en.wikipedia.org/wiki/Philosophy_of_mathematics#Formalism "Philosophy of mathematics") and Wittgenstein propounding his view that mathematics does not discover any absolute truths, but rather invents them. ### Cryptanalysis During the Second World War, Turing was a leading participant in the breaking of German ciphers at [Bletchley Park](https://en.wikipedia.org/wiki/Bletchley_Park "Bletchley Park"). The historian and wartime codebreaker [Asa Briggs](https://en.wikipedia.org/wiki/Asa_Briggs "Asa Briggs") has said, "You needed exceptional talent, you needed genius at Bletchley and Turing's was that genius." From September 1938, Turing worked part-time with the [Government Code and Cypher School](https://en.wikipedia.org/wiki/Government_Code_and_Cypher_School "Government Code and Cypher School") (GC&CS), the British codebreaking organisation. He concentrated on [cryptanalysis of the Enigma cipher machine](https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma "Cryptanalysis of the Enigma") used by [Nazi Germany](https://en.wikipedia.org/wiki/Nazi_Germany "Nazi Germany"), together with [Dilly Knox](https://en.wikipedia.org/wiki/Dilly_Knox "Dilly Knox"), a senior GC&CS codebreaker. Soon after the July 1939 meeting near [Warsaw](https://en.wikipedia.org/wiki/Warsaw "Warsaw") at which the [Polish Cipher Bureau](https://en.wikipedia.org/wiki/Polish_Cipher_Bureau "Polish Cipher Bureau") gave the British and French details of the wiring of [Enigma machine's rotors](https://en.wikipedia.org/wiki/Enigma_rotor_details "Enigma rotor details") and their method of decrypting [Enigma machine](https://en.wikipedia.org/wiki/Enigma_machine "Enigma machine")'s messages, Turing and Knox developed a broader solution. The Polish method relied on an insecure [indicator](https://en.wikipedia.org/wiki/Cryptanalysis#Indicator "Cryptanalysis") procedure that the Germans were likely to change, which they in fact did in May 1940. Turing's approach was more general, using [crib-based decryption](https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma#Crib-based_decryption "Cryptanalysis of the Enigma") for which he produced the functional specification of the [bombe](https://en.wikipedia.org/wiki/Bombe "Bombe") (an improvement on the Polish [Bomba](https://en.wikipedia.org/wiki/Bomba_\(cryptography\) "Bomba (cryptography)")). [![](https://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Turing_flat.jpg/250px-Turing_flat.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Turing_flat.jpg) Two cottages in the stable yard at [Bletchley Park](https://en.wikipedia.org/wiki/Bletchley_Park "Bletchley Park"). Turing worked here in 1939 and 1940, before moving to [Hut 8](https://en.wikipedia.org/wiki/Hut_8 "Hut 8"). On 4 September 1939, the day after the UK declared war on Germany, Turing reported to Bletchley Park, the wartime station of GC&CS. Like all others who came to Bletchley, he was required to sign the [Official Secrets Act](https://en.wikipedia.org/wiki/Official_Secrets_Act_1939 "Official Secrets Act 1939"), in which he agreed not to disclose anything about his work at Bletchley, with severe legal penalties for violating the Act. Specifying the bombe was the first of five major cryptanalytical advances that Turing made during the war. The others were: deducing the indicator procedure used by the German navy; developing a statistical procedure dubbed _[Banburismus](https://en.wikipedia.org/wiki/Banburismus "Banburismus")_ for making much more efficient use of the bombes; developing a procedure dubbed _[Turingery](https://en.wikipedia.org/wiki/Turingery "Turingery")_ for working out the cam settings of the wheels of the [Lorenz SZ 40/42](https://en.wikipedia.org/wiki/Lorenz_SZ_40/42 "Lorenz SZ 40/42") (_Tunny_) cipher machine and, towards the end of the war, the development of a portable [secure voice](https://en.wikipedia.org/wiki/Secure_voice "Secure voice") scrambler at [Hanslope Park](https://en.wikipedia.org/wiki/Her_Majesty's_Government_Communications_Centre "Her Majesty's Government Communications Centre") that was codenamed Delilah. By using statistical techniques to optimise the trial of different possibilities in the code breaking process, Turing made an innovative contribution to the subject. He wrote two papers discussing mathematical approaches, titled _The Applications of Probability to Cryptography_ and _Paper on Statistics of Repetitions_, which were of such value to GC&CS and its successor [GCHQ](https://en.wikipedia.org/wiki/GCHQ "GCHQ") that they were not released to the [UK National Archives](https://en.wikipedia.org/wiki/The_National_Archives_\(United_Kingdom\) "The National Archives (United Kingdom)") until April 2012, shortly before the centenary of his birth. A GCHQ mathematician, "who identified himself only as Richard," said at the time that the fact that the contents had been restricted under the Official Secrets Act for some 70 years demonstrated their importance, and their relevance to post-war cryptanalysis: > \[He\] said the fact that the contents had been restricted "shows what a tremendous importance it has in the foundations of our subject". ... The papers detailed using "mathematical analysis to try and determine which are the more likely settings so that they can be tried as quickly as possible". ... Richard said that GCHQ had now "squeezed the juice" out of the two papers and was "happy for them to be released into the public domain". Turing had a reputation for eccentricity at Bletchley Park. He was known to his colleagues as "Prof" and his treatise on Enigma was known as the "Prof's Book". According to historian [Ronald Lewin](https://en.wikipedia.org/wiki/Ronald_Lewin "Ronald Lewin"), [Jack Good](https://en.wikipedia.org/wiki/I.J._Good "I.J. Good"), a cryptanalyst who worked with Turing, said of his colleague: > In the first week of June each year he would get a bad attack of hay fever, and he would cycle to the office wearing a service gas mask to keep the pollen off. His bicycle had a fault: the chain would come off at regular intervals. Instead of having it mended he would count the number of times the pedals went round and would get off the bicycle in time to adjust the chain by hand. Another of his eccentricities is that he chained his mug to the radiator pipes to prevent it being stolen. [Peter Hilton](https://en.wikipedia.org/wiki/Peter_Hilton "Peter Hilton") recounted his experience working with Turing in [Hut 8](https://en.wikipedia.org/wiki/Hut_8 "Hut 8") in his "Reminiscences of Bletchley Park" from _A Century of Mathematics in America:_ > It is a rare experience to meet an authentic genius. Those of us privileged to inhabit the world of scholarship are familiar with the intellectual stimulation furnished by talented colleagues. We can admire the ideas they share with us and are usually able to understand their source; we may even often believe that we ourselves could have created such concepts and originated such thoughts. However, the experience of sharing the intellectual life of a genius is entirely different; one realizes that one is in the presence of an intelligence, a sensibility of such profundity and originality that one is filled with wonder and excitement. Alan Turing was such a genius, and those, like myself, who had the astonishing and unexpected opportunity, created by the strange exigencies of the Second World War, to be able to count Turing as colleague and friend will never forget that experience, nor can we ever lose its immense benefit to us. While working at Bletchley, Turing, who was a talented [long-distance runner](https://en.wikipedia.org/wiki/Long-distance_running "Long-distance running"), occasionally ran the 40 miles (64 km) to London when he was needed for meetings, and he was capable of world-class marathon standards. Turing tried out for the [1948 British Olympic team](https://en.wikipedia.org/wiki/Great_Britain_at_the_1948_Summer_Olympics "Great Britain at the 1948 Summer Olympics"), but he was hampered by an injury. His tryout time for the marathon was only 11 minutes slower than British silver medallist [Thomas Richards](https://en.wikipedia.org/wiki/Tom_Richards_\(athlete\) "Tom Richards (athlete)")' Olympic race time of 2 hours 35 minutes. He was Walton Athletic Club's best runner, a fact discovered when he passed the group while running alone. When asked why he ran so hard in training he replied: > I have such a stressful job that the only way I can get it out of my mind is by running hard; it's the only way I can get some release. Due to the challenges answering questions concerning what an outcome would have been if a historical event did or did not occur (the realm of [counterfactual history](https://en.wikipedia.org/wiki/Counterfactual_history "Counterfactual history")), it is hard to estimate the precise effect Ultra intelligence had on the war. However, official war historian [Harry Hinsley](https://en.wikipedia.org/wiki/Harry_Hinsley "Harry Hinsley") estimated that this work shortened the war in Europe by more than two years. He added the caveat that this did not account for the use of the atomic bomb and other eventualities. At the end of the war, a memo was sent to all those who had worked at Bletchley Park, reminding them that the code of silence dictated by the Official Secrets Act did not end with the war but would continue indefinitely. Thus, even though Turing was appointed an [Officer of the Order of the British Empire](https://en.wikipedia.org/wiki/Order_of_the_British_Empire "Order of the British Empire") (OBE) in 1946 by King [George VI](https://en.wikipedia.org/wiki/George_VI "George VI") for his wartime services, his work remained secret for many years. ### Bombe Within weeks of arriving at Bletchley Park, Turing had specified an electromechanical machine called the [bombe](https://en.wikipedia.org/wiki/Bombe "Bombe"), which could break Enigma more effectively than the Polish _[bomba kryptologiczna](https://en.wikipedia.org/wiki/Bomba_\(cryptography\) "Bomba (cryptography)")_, from which its name was derived. The bombe, with an enhancement suggested by mathematician [Gordon Welchman](https://en.wikipedia.org/wiki/Gordon_Welchman "Gordon Welchman"), became one of the primary tools, and the major automated one, used to attack Enigma-enciphered messages. [![](https://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Bombe-rebuild.jpg/250px-Bombe-rebuild.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Bombe-rebuild.jpg) A working replica of a [bombe](https://en.wikipedia.org/wiki/Bombe "Bombe") now at [The National Museum of Computing](https://en.wikipedia.org/wiki/The_National_Museum_of_Computing "The National Museum of Computing") on Bletchley Park The bombe searched for possible correct settings used for an Enigma message (i.e., rotor order, rotor settings and plugboard settings) using a suitable _[crib](https://en.wikipedia.org/wiki/Crib_\(cryptanalysis\) "Crib (cryptanalysis)")_: a fragment of probable [plaintext](https://en.wikipedia.org/wiki/Plaintext "Plaintext"). For each possible setting of the rotors (which had on the order of 1019 states, or 1022 states for the four-rotor U-boat variant), the bombe performed a chain of logical deductions based on the crib, implemented [electromechanically](https://en.wikipedia.org/wiki/Electromechanics "Electromechanics"). The bombe detected when a contradiction had occurred and ruled out that setting, moving on to the next. Most of the possible settings would cause contradictions and be discarded, leaving only a few to be investigated in detail. A contradiction would occur when an enciphered letter would be turned back into the same plaintext letter, which was impossible with the Enigma. The first bombe was installed on 18 March 1940. #### Action This Day Main article: [Action This Day (memo)](https://en.wikipedia.org/wiki/Action_This_Day_\(memo\) "Action This Day (memo)") By late 1941, Turing and his fellow cryptanalysts Welchman, [Hugh Alexander](https://en.wikipedia.org/wiki/Conel_Hugh_O'Donel_Alexander "Conel Hugh O'Donel Alexander") and [Stuart Milner-Barry](https://en.wikipedia.org/wiki/Stuart_Milner-Barry "Stuart Milner-Barry") were frustrated. Building on the [work of the Poles](https://en.wikipedia.org/wiki/Biuro_Szyfr%C3%B3w#Gift_to_allies "Biuro Szyfrów"), they had set up a good working system for decrypting Enigma signals, but their limited staff and bombes meant they could not translate all the signals. In the summer, they had considerable success, and shipping losses had fallen to under 100,000 tons a month; however, they badly needed more resources to keep abreast of German adjustments. They had tried to get more people and fund more bombes through the proper channels, but had failed. On 28 October they wrote directly to [Winston Churchill](https://en.wikipedia.org/wiki/Winston_Churchill "Winston Churchill") explaining their difficulties, with Turing as the first named. They emphasised how small their need was compared with the vast expenditure of men and money by the forces and compared with the level of assistance they could offer to the forces. As [Andrew Hodges](https://en.wikipedia.org/wiki/Andrew_Hodges "Andrew Hodges"), biographer of Turing, later wrote, "This letter had an electric effect." Churchill wrote a memo to [General Ismay](https://en.wikipedia.org/wiki/Hastings_Ismay,_1st_Baron_Ismay "Hastings Ismay, 1st Baron Ismay"), which read: "ACTION THIS DAY. Make sure they have all they want on extreme priority and report to me that this has been done." On 18 November, the chief of the secret service reported that every possible measure was being taken. The cryptographers at Bletchley Park did not know of the Prime Minister's response, but as Milner-Barry recalled, "All that we did notice was that almost from that day the rough ways began miraculously to be made smooth." More than two hundred bombes were in operation by the end of the war. ### Hut 8 and the naval Enigma [![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Turing-statue-Bletchley_14.jpg/250px-Turing-statue-Bletchley_14.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Turing-statue-Bletchley_14.jpg) Statue of Turing holding an Enigma machine by [Stephen Kettle](https://en.wikipedia.org/wiki/Stephen_Kettle "Stephen Kettle") at Bletchley Park, commissioned by [Sidney Frank](https://en.wikipedia.org/wiki/Sidney_Frank "Sidney Frank"), built from half a million pieces of Welsh slate Turing decided to tackle the particularly difficult problem of cracking the [German naval use of Enigma](https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma#German_Naval_Enigma "Cryptanalysis of the Enigma") "because no one else was doing anything about it and I could have it to myself". In December 1939, Turing solved the essential part of the naval [indicator](https://en.wikipedia.org/wiki/Enigma_machine#Indicator "Enigma machine") system, which was more complex than the indicator systems used by the other services. That same night, he also conceived of the idea of _[Banburismus](https://en.wikipedia.org/wiki/Banburismus "Banburismus")_, a sequential statistical technique (what [Abraham Wald](https://en.wikipedia.org/wiki/Abraham_Wald "Abraham Wald") later called [sequential analysis](https://en.wikipedia.org/wiki/Sequential_analysis "Sequential analysis")) to assist in breaking the naval Enigma, "though I was not sure that it would work in practice, and was not, in fact, sure until some days had actually broken". For this, he invented a measure of weight of evidence that he called the _[ban](https://en.wikipedia.org/wiki/Ban_\(unit\) "Ban (unit)")_. _Banburismus_ could rule out certain sequences of the Enigma rotors, substantially reducing the time needed to test settings on the bombes. Later this sequential process of accumulating sufficient weight of evidence using decibans (one tenth of a ban) was used in [cryptanalysis of the Lorenz cipher](https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher "Cryptanalysis of the Lorenz cipher"). Turing travelled to the United States in November 1942 and worked with US Navy cryptanalysts on the naval Enigma and bombe construction in Washington. He also visited their [Computing Machine Laboratory](https://en.wikipedia.org/wiki/United_States_Naval_Computing_Machine_Laboratory "United States Naval Computing Machine Laboratory") in [Dayton, Ohio](https://en.wikipedia.org/wiki/Dayton,_Ohio "Dayton, Ohio"). Turing's reaction to the American bombe design was far from enthusiastic: > The American Bombe programme was to produce 336 Bombes, one for each wheel order. I used to smile inwardly at the conception of Bombe hut routine implied by this programme, but thought that no particular purpose would be served by pointing out that we would not really use them in that way. Their test (of commutators) can hardly be considered conclusive as they were not testing for the bounce with electronic stop finding devices. Nobody seems to be told about rods or offiziers or banburismus unless they are really going to do something about it. During this trip, he also assisted at [Bell Labs](https://en.wikipedia.org/wiki/Bell_Labs "Bell Labs") with the development of [secure speech](https://en.wikipedia.org/wiki/Secure_speech "Secure speech") devices. He returned to Bletchley Park in March 1943. During his absence, [Hugh Alexander](https://en.wikipedia.org/wiki/Colonel_Hugh_O'Donel_Alexander "Colonel Hugh O'Donel Alexander") had officially assumed the position of head of Hut 8, although Alexander had been _de facto_ head for some time (Turing having little interest in the day-to-day running of the section). Turing became a general consultant for cryptanalysis at Bletchley Park. Alexander wrote of Turing's contribution: > There should be no question in anyone's mind that Turing's work was the biggest factor in Hut 8's success. In the early days, he was the only cryptographer who thought the problem worth tackling and not only was he primarily responsible for the main theoretical work within the Hut, but he also shared with Welchman and Keen the chief credit for the invention of the bombe. It is always difficult to say that anyone is 'absolutely indispensable', but if anyone was indispensable to Hut 8, it was Turing. The pioneer's work always tends to be forgotten when experience and routine later make everything seem easy and many of us in Hut 8 felt that the magnitude of Turing's contribution was never fully realised by the outside world. ### Turingery In July 1942, Turing devised a technique termed _[Turingery](https://en.wikipedia.org/wiki/Turingery "Turingery")_ (or jokingly _Turingismus_) for use against the [Lorenz cipher](https://en.wikipedia.org/wiki/Lorenz_cipher "Lorenz cipher") messages produced by the Germans' new _Geheimschreiber_ (secret writer) machine. This was a [teleprinter](https://en.wikipedia.org/wiki/Teleprinter "Teleprinter") [rotor cipher attachment](https://en.wikipedia.org/wiki/Rotor_machine "Rotor machine") codenamed _Tunny_ at Bletchley Park. Turingery was a method of _wheel-breaking_, i.e., a procedure for working out the cam settings of Tunny's wheels. He also introduced the Tunny team to [Tommy Flowers](https://en.wikipedia.org/wiki/Tommy_Flowers "Tommy Flowers") who, under the guidance of [Max Newman](https://en.wikipedia.org/wiki/Max_Newman "Max Newman"), went on to build the [Colossus computer](https://en.wikipedia.org/wiki/Colossus_computer "Colossus computer"), the world's first programmable digital electronic computer, which replaced a simpler prior machine (the [Heath Robinson](https://en.wikipedia.org/wiki/Heath_Robinson_\(codebreaking_machine\) "Heath Robinson (codebreaking machine)")), and whose superior speed allowed the statistical decryption techniques to be applied usefully to the messages. Some have mistakenly said that Turing was a key figure in the design of the Colossus computer. Turingery and the statistical approach of Banburismus undoubtedly fed into the thinking about [cryptanalysis of the Lorenz cipher](https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher "Cryptanalysis of the Lorenz cipher"), but he was not directly involved in the Colossus development. ### Delilah Following his work at [Bell Labs](https://en.wikipedia.org/wiki/Bell_Labs "Bell Labs") in the US, Turing pursued the idea of electronic enciphering of speech in the telephone system. In the latter part of the war, he moved to work for the Secret Service's Radio Security Service (later [HMGCC](https://en.wikipedia.org/wiki/Her_Majesty's_Government_Communications_Centre "Her Majesty's Government Communications Centre")) at [Hanslope Park](https://en.wikipedia.org/wiki/Hanslope_Park "Hanslope Park"). At the park, he further developed his knowledge of electronics with the assistance of [REME](https://en.wikipedia.org/wiki/Royal_Electrical_and_Mechanical_Engineers "Royal Electrical and Mechanical Engineers") officer Donald Bayley. Together they undertook the design and construction of a portable [secure voice](https://en.wikipedia.org/wiki/Secure_voice "Secure voice") communications machine codenamed _[Delilah](https://en.wikipedia.org/wiki/Delilah_\(voice_encryption\)?action=edit&redlink=1 "Delilah (voice encryption)")_. The machine was intended for different applications, but it lacked the capability for use with long-distance radio transmissions. In any case, Delilah was completed too late to be used during the war. Though the system worked fully, with Turing demonstrating it to officials by encrypting and decrypting a recording of a [Winston Churchill](https://en.wikipedia.org/wiki/Winston_Churchill "Winston Churchill") speech, Delilah was not adopted for use. Turing also consulted with Bell Labs on the development of [SIGSALY](https://en.wikipedia.org/wiki/SIGSALY "SIGSALY"), a secure voice system that was used in the later years of the war. ### Early computers and the Turing test [![](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Alan_Turing_78_High_Street_Hampton_blue_plaque.jpg/250px-Alan_Turing_78_High_Street_Hampton_blue_plaque.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_78_High_Street_Hampton_blue_plaque.jpg) Plaque, 78 High Street, [Hampton](https://en.wikipedia.org/wiki/Hampton,_London "Hampton, London") Between 1945 and 1947, Turing lived in [Hampton](https://en.wikipedia.org/wiki/Hampton,_London "Hampton, London"), London, while he worked on the design of the [ACE](https://en.wikipedia.org/wiki/ACE_\(computer\) "ACE (computer)") (Automatic Computing Engine) at the [National Physical Laboratory (NPL)](https://en.wikipedia.org/wiki/National_Physical_Laboratory_\(United_Kingdom\) "National Physical Laboratory (United Kingdom)"). He presented a paper on 19 February 1946, which was the first detailed design of a [stored-program computer](https://en.wikipedia.org/wiki/Stored-program_computer "Stored-program computer"). [Von Neumann](https://en.wikipedia.org/wiki/John_von_Neumann "John von Neumann")'s incomplete _[First Draft of a Report on the EDVAC](https://en.wikipedia.org/wiki/First_Draft_of_a_Report_on_the_EDVAC "First Draft of a Report on the EDVAC")_ had predated Turing's paper, but it was much less detailed and, according to [John R. Womersley](https://en.wikipedia.org/wiki/John_R._Womersley "John R. Womersley"), Superintendent of the NPL Mathematics Division, it "contains a number of ideas which are Dr. Turing's own". Although ACE was a feasible design, the effect of the [Official Secrets Act](https://en.wikipedia.org/wiki/Official_Secrets_Act_1939 "Official Secrets Act 1939") surrounding the wartime work at Bletchley Park made it impossible for Turing to explain the basis of his analysis of how a computer installation involving human operators would work. This led to delays in starting the project and he became disillusioned. In late 1947 he returned to Cambridge for a sabbatical year during which he produced a seminal work on _Intelligent Machinery_ that was not published in his lifetime. While he was at Cambridge, the [Pilot ACE](https://en.wikipedia.org/wiki/Pilot_ACE "Pilot ACE") was being built in his absence. It executed its first program on 10 May 1950, and a number of later computers around the world owe much to it, including the [English Electric DEUCE](https://en.wikipedia.org/wiki/English_Electric_DEUCE "English Electric DEUCE") and the American [Bendix G-15](https://en.wikipedia.org/wiki/Bendix_G-15 "Bendix G-15"). The full version of Turing's ACE was not built until after his death. According to the memoirs of the German computer pioneer [Heinz Billing](https://en.wikipedia.org/wiki/Heinz_Billing "Heinz Billing") from the [Max Planck Institute for Physics](https://en.wikipedia.org/wiki/Max_Planck_Institute_for_Physics "Max Planck Institute for Physics"), published by Genscher, Düsseldorf, there was a meeting between Turing and [Konrad Zuse](https://en.wikipedia.org/wiki/Konrad_Zuse "Konrad Zuse"). It took place in [Göttingen](https://en.wikipedia.org/wiki/G%C3%B6ttingen "Göttingen") in 1947. The interrogation had the form of a colloquium. Participants were Womersley, Turing, Porter from England and a few German researchers like Zuse, Walther, and Billing (for more details see Herbert Bruderer, _Konrad Zuse und die Schweiz_). [![](https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Alan_Turing_Blue_Plaque%2C_University_of_Manchester.jpg/250px-Alan_Turing_Blue_Plaque%2C_University_of_Manchester.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_Blue_Plaque,_University_of_Manchester.jpg) A [blue plaque](https://en.wikipedia.org/wiki/Blue_plaque "Blue plaque") commemorating Alan Turing's work at the [University of Manchester](https://en.wikipedia.org/wiki/University_of_Manchester "University of Manchester") where he was a [Reader](https://en.wikipedia.org/wiki/Reader_\(academic_rank\) "Reader (academic rank)") from 1948 to 1954 In 1948, Turing was appointed [reader](https://en.wikipedia.org/wiki/Reader_\(academic_rank\) "Reader (academic rank)") in the [Mathematics Department](https://en.wikipedia.org/wiki/School_of_Mathematics,_University_of_Manchester "School of Mathematics, University of Manchester") at the [University of Manchester](https://en.wikipedia.org/wiki/University_of_Manchester "University of Manchester"). He lived at "Copper Folly", 43 Adlington Road, in [Wilmslow](https://en.wikipedia.org/wiki/Wilmslow "Wilmslow"). A year later, he became deputy director of the Computing Machine Laboratory, where he worked on software for one of the earliest [stored-program](https://en.wikipedia.org/wiki/Von_Neumann_architecture "Von Neumann architecture") computers—the [Manchester Mark 1](https://en.wikipedia.org/wiki/Manchester_Mark_1 "Manchester Mark 1"). Turing wrote the first version of the Programmer's Manual for this machine, was elected to membership of the [Manchester Literary and Philosophical Society](https://en.wikipedia.org/wiki/Manchester_Literary_and_Philosophical_Society "Manchester Literary and Philosophical Society"), and was recruited by Ferranti as a consultant in the development of their commercialised machine, the Ferranti Mark 1. He continued to be paid consultancy fees by Ferranti until his death. During this time, he continued to do more abstract work in mathematics, and in "[Computing Machinery and Intelligence](https://en.wikipedia.org/wiki/Computing_Machinery_and_Intelligence "Computing Machinery and Intelligence")", Turing addressed the problem of [artificial intelligence](https://en.wikipedia.org/wiki/Artificial_intelligence "Artificial intelligence"), and proposed an experiment that became known as the [Turing test](https://en.wikipedia.org/wiki/Turing_test "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 a human interrogator could not tell it apart, through conversation, from a human being. In the paper, Turing suggested that rather than building a program to simulate the adult mind, it would be better to produce a simpler one to simulate a child's mind and then to subject it to a course of education. A [reversed](https://en.wikipedia.org/wiki/Turing_test#Reverse_Turing_test_and_CAPTCHA "Turing test") form of the Turing test is widely used on the Internet; the [CAPTCHA](https://en.wikipedia.org/wiki/CAPTCHA "CAPTCHA") test is intended to determine whether the user is a human or a computer. In 1948, Turing, working with his former undergraduate colleague, [D.G. Champernowne](https://en.wikipedia.org/wiki/D.G._Champernowne "D.G. Champernowne"), began writing a [chess](https://en.wikipedia.org/wiki/Chess "Chess") program for a computer that did not yet exist. By 1950, the program was completed and dubbed the [Turochamp](https://en.wikipedia.org/wiki/Turochamp "Turochamp"). In 1952, he tried to implement it on a [Ferranti Mark 1](https://en.wikipedia.org/wiki/Ferranti_Mark_1 "Ferranti Mark 1"), but lacking enough power, the computer was unable to execute the program. Instead, Turing "ran" the program by flipping through the pages of the algorithm and carrying out its instructions on a chessboard, taking about half an hour per move. The game was recorded. According to [Garry Kasparov](https://en.wikipedia.org/wiki/Garry_Kasparov "Garry Kasparov"), Turing's program "played a recognizable game of chess". The program lost to Turing's colleague [Alick Glennie](https://en.wikipedia.org/wiki/Alick_Glennie "Alick Glennie"), although it is said that it won a game against Champernowne's wife, Isabel. His Turing test was a significant, characteristically provocative, and lasting contribution to the debate regarding artificial intelligence, which continues after more than half a century. ### Pattern formation and mathematical biology When Turing was 39 years old in 1951, he turned to [mathematical biology](https://en.wikipedia.org/wiki/Mathematical_and_theoretical_biology "Mathematical and theoretical biology"), finally publishing his masterpiece "[The Chemical Basis of Morphogenesis](https://en.wikipedia.org/wiki/The_Chemical_Basis_of_Morphogenesis "The Chemical Basis of Morphogenesis")" in January 1952. He was interested in [morphogenesis](https://en.wikipedia.org/wiki/Morphogenesis "Morphogenesis"), the development of patterns and shapes in biological organisms. He suggested that a system of chemicals reacting with each other and diffusing across space, termed a [reaction–diffusion system](https://en.wikipedia.org/wiki/Reaction%E2%80%93diffusion_system "Reaction–diffusion system"), could account for "the main phenomena of morphogenesis". He used systems of [partial differential equations](https://en.wikipedia.org/wiki/Partial_differential_equations "Partial differential equations") to model catalytic chemical reactions. For example, if a catalyst A is required for a certain chemical reaction to take place, and if the reaction produced more of the catalyst A, then we say that the reaction is [autocatalytic](https://en.wikipedia.org/wiki/Autocatalytic "Autocatalytic"), and there is positive feedback that can be modelled by nonlinear differential equations. Turing discovered that patterns could be created if the chemical reaction not only produced catalyst A, but also produced an inhibitor B that slowed down the production of A. If A and B then diffused through the container at different rates, then you could have some regions where A dominated and some where B did. To calculate the extent of this, Turing would have needed a powerful computer, but these were not so freely available in 1951, so he had to use linear approximations to solve the equations by hand. These calculations gave the right qualitative results, and produced, for example, a uniform mixture that oddly enough had regularly spaced fixed red spots. The Russian biochemist [Boris Belousov](https://en.wikipedia.org/wiki/Boris_Pavlovich_Belousov "Boris Pavlovich Belousov") had performed experiments with similar results, but could not get his papers published because of the contemporary prejudice that any such thing violated the [second law of thermodynamics](https://en.wikipedia.org/wiki/Second_law_of_thermodynamics "Second law of thermodynamics"). Belousov was not aware of Turing's paper in the _[Philosophical Transactions of the Royal Society](https://en.wikipedia.org/wiki/Philosophical_Transactions_of_the_Royal_Society "Philosophical Transactions of the Royal Society")_. Although published before the structure and role of [DNA](https://en.wikipedia.org/wiki/DNA "DNA") was understood, Turing's work on morphogenesis remains relevant today and is considered a seminal piece of work in mathematical biology. Some of this work aimed to understand plant [phyllotaxy](https://en.wikipedia.org/wiki/Phyllotaxis "Phyllotaxis"), specifically how plant [primordia](https://en.wikipedia.org/wiki/Primordium "Primordium") form in a ring around the apical [meristem](https://en.wikipedia.org/wiki/Meristem "Meristem") during plant growth and development, forming Fibonacci series. One of the early applications of Turing's paper was the work by James Murray explaining spots and stripes on the fur of cats, large and small. Further research in the area suggests that Turing's work can partially explain the growth of "feathers, hair follicles, the branching pattern of lungs, and even the left-right asymmetry that puts the heart on the left side of the chest". In 2012, Sheth, et al. found that in mice, removal of [Hox genes](https://en.wikipedia.org/wiki/Hox_genes "Hox genes") causes an increase in the number of digits without an increase in the overall size of the limb, suggesting that Hox genes control digit formation by tuning the wavelength of a Turing-type mechanism. Later papers were not available until _Collected Works of A. M. Turing_ was published in 1992. A study conducted in 2023 confirmed Turing's mathematical model hypothesis. Presented by the [American Physical Society](https://en.wikipedia.org/wiki/American_Physical_Society "American Physical Society"), the experiment involved growing [chia seeds](https://en.wikipedia.org/wiki/Chia_seed "Chia seed") in even layers within trays, later adjusting the available moisture. Researchers experimentally tweaked the factors which appear in the Turing equations, and, as a result, patterns resembling those seen in natural environments emerged. This is believed to be the first time that experiments with living vegetation have verified Turing's mathematical insight. ### Ratio Club and other cybernetics contacts The [Ratio Club](https://en.wikipedia.org/wiki/Ratio_Club "Ratio Club") was a London [dining club](https://en.wikipedia.org/wiki/Dining_club "Dining club") for researchers (mostly biologists) with interests in [cybernetics](https://en.wikipedia.org/wiki/Cybernetics "Cybernetics") (which encompassed [neuroscience](https://en.wikipedia.org/wiki/Neuroscience "Neuroscience"), artificial intelligence and computing), "undoubtedly the most intellectually powerful grouping of British scientists interested in cybernetics" according to [Phil Husbands](https://en.wikipedia.org/wiki/Phil_Husbands "Phil Husbands") and [Owen Holland](https://en.wikipedia.org/wiki/Owen_Holland_\(academic\) "Owen Holland (academic)"). At the first meeting on 4 September 1949 it was agreed to invite Turing to join. He accepted, giving his introductory talk at the 21 April 1950 meeting. He gave later talks based on both his "Computing Machinery and Intelligence" and "Chemical Basis of Morphogenesis" papers. On a 1949 visit to Britain to attend a conference on psychiatry American cybernetician [Warren McCulloch](https://en.wikipedia.org/wiki/Warren_McCulloch "Warren McCulloch") made a trip to Manchester to meet Turing (who may have been unimpressed). ## Personal life ### Treasure In the 1940s, Turing became worried about losing his savings in the event of a German invasion. To protect it, he bought two [silver bars](https://en.wikipedia.org/wiki/Silver_bar "Silver bar") weighing 3,200 oz (90 kg) and worth £250 (in 2022, £8,000 [adjusted for inflation](https://en.wikipedia.org/wiki/Adjusted_for_inflation "Adjusted for inflation"), £48,000 at spot price) and buried them in a wood near Bletchley Park. Upon returning to dig them up, Turing found that he was unable to break his own code describing where exactly he had hidden them. This, along with the fact that the area had been renovated, meant that he never regained the silver. ### Engagement In 1941, Turing proposed marriage to Hut 8 colleague [Joan Clarke](https://en.wikipedia.org/wiki/Joan_Clarke "Joan Clarke"), a fellow mathematician and cryptanalyst, but their engagement was short-lived. After admitting his homosexuality to his fiancée, who was reportedly "unfazed" by the revelation, Turing decided that he could not go through with the marriage. ### Chess Turing invented a hybrid chess sport, earlier than [chess boxing](https://en.wikipedia.org/wiki/Chess_boxing "Chess boxing"), referred to as _round-the-house chess_, one player makes a chess move, then that player runs around the house, and the other player must make a chess move before the first player returns. ### Homosexuality and indecency conviction [![](https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Dancehouse.jpg/250px-Dancehouse.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Dancehouse.jpg) The [Dancehouse Theatre](https://en.wikipedia.org/wiki/Dancehouse "Dancehouse"), formerly the Regal Cinema, pictured in 2006, outside of which Turing met Arnold Murray [![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f6/Alan_Turing%27s_House_from_1950_to_1954.jpg/250px-Alan_Turing%27s_House_from_1950_to_1954.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing's_House_from_1950_to_1954.jpg) The house where Alan Turing lived in his final years from 1950 to 1954 at 43 Adlington Road in [Wilmslow](https://en.wikipedia.org/wiki/Wilmslow "Wilmslow") In December 1951, Turing met Arnold Murray, a 19-year-old unemployed man. Turing was walking along Manchester's [Oxford Road](https://en.wikipedia.org/wiki/Wilmslow_Road "Wilmslow Road") when he met Murray just outside the [Regal Cinema](https://en.wikipedia.org/wiki/Dancehouse "Dancehouse") and invited him to lunch. The two agreed to meet again and in January 1952 began an intimate relationship. On 23 January, Turing's house in Wilmslow was burgled. Murray told Turing that he and the burglar were acquainted, and Turing reported the crime to the police. During the investigation, he acknowledged a sexual relationship with Murray. Homosexual acts were criminal offences in the United Kingdom at that time, and both men were charged with "[gross indecency](https://en.wikipedia.org/wiki/Gross_indecency "Gross indecency")" under [Section 11](https://en.wikipedia.org/wiki/Criminal_Law_Amendment_Act_1885#Section_11 "Criminal Law Amendment Act 1885") of the [Criminal Law Amendment Act 1885](https://en.wikipedia.org/wiki/Criminal_Law_Amendment_Act_1885 "Criminal Law Amendment Act 1885"). Initial [committal proceedings](https://en.wikipedia.org/wiki/Committal_procedure "Committal procedure") for the trial were held on 27 February during which Turing's solicitor "reserved his defence", i.e., did not argue or provide evidence against the allegations. The proceedings were held at the [Sessions House](https://en.wikipedia.org/wiki/Sessions_House,_Knutsford "Sessions House, Knutsford") in [Knutsford](https://en.wikipedia.org/wiki/Knutsford "Knutsford"). Turing was later convinced by the advice of his brother and his own solicitor, and he entered a plea of guilty. The case, _[Regina](https://en.wikipedia.org/wiki/Elizabeth_II "Elizabeth II") v. Turing and Murray,_ was brought to trial on 31 March 1952. Turing's barrister pushed for him not to be incarcerated, and he was sentenced to 12 months' probation. His probation would be conditional on his agreement to undergo organotherapy or '[chemical castration](https://en.wikipedia.org/wiki/Chemical_castration "Chemical castration")' [Manchester Royal Infirmary](https://en.wikipedia.org/wiki/Manchester_Royal_Infirmary "Manchester Royal Infirmary"), a process which induces [hormonal](https://en.wikipedia.org/wiki/Hormone "Hormone") physical changes with the aim of reducing [libido](https://en.wikipedia.org/wiki/Libido "Libido"). In a letter, Turing wrote that "no doubt I shall emerge from it all a different man, but quite who I've not found out". Murray was given a conditional discharge. Turing was given injections of what was then called [stilboestrol](https://en.wikipedia.org/wiki/Stilbestrol "Stilbestrol") (now known as [diethylstilbestrol](https://en.wikipedia.org/wiki/Diethylstilbestrol "Diethylstilbestrol") or DES), a synthetic [oestrogen](https://en.wikipedia.org/wiki/Oestrogen "Oestrogen"). The treatment rendered him [impotent](https://en.wikipedia.org/wiki/Impotence "Impotence") and caused [breast tissue to form](https://en.wikipedia.org/wiki/Gynaecomastia "Gynaecomastia"), the latter of which Turing found somewhat amusing according to his friends. The hormonal injections did not appear to have worked as expected, as Turing was still finding himself attracted to men. Turing's conviction led to the removal of his security clearance and barred him from continuing with his cryptographic consultancy for [GCHQ](https://en.wikipedia.org/wiki/GCHQ "GCHQ"), the British [signals intelligence](https://en.wikipedia.org/wiki/Signals_intelligence "Signals intelligence") agency that had evolved from GC&CS in 1946, though he kept his academic post. His trial took place only months after the defection to the Soviet Union of [Guy Burgess](https://en.wikipedia.org/wiki/Guy_Burgess "Guy Burgess") and [Donald Maclean](https://en.wikipedia.org/wiki/Donald_Maclean_\(spy\) "Donald Maclean (spy)"), in summer 1951, after which the Foreign Office started to consider anyone known to be homosexual as a potential security risk. Turing was denied entry into the United States after his conviction in 1952, but was free to visit other European countries. In the summer of 1952 he visited Norway, which was more tolerant of homosexuals. Among the various men he met there was one named Kjell Carlson. Kjell intended to visit Turing in the UK, but the authorities intercepted Kjell's postcard detailing his travel arrangements and were able to intercept and deport him before the two could meet. It was also during this time that Turing started consulting a psychiatrist, Franz Greenbaum, with whom he got on well and who subsequently became a family friend. #### "Pryce's Buoy" Circa 1953, Turing wrote an unfinished comedic gay short story titled "Pryce's Buoy", which was unearthed in July 2026. It was notable for revealing his "playful side". Largely autobiographical, the narrative piece detailed an erotic encouter between a male youth in need of money and a wealthy older theoretical scientist looking for casual sex. The title is a sexual [pun](https://en.wikipedia.org/wiki/Pun "Pun") of a fictional math equation, described by Turing within the story, sharing similarities with the [Turing test](https://en.wikipedia.org/wiki/Turing_test "Turing test"). Literature professor Sarah Dillon of [Cambridge University](https://en.wikipedia.org/wiki/University_of_Cambridge "University of Cambridge") unearthed the story in 2026 by transcribing Turing's handwritten prose from archived pages and researching its origins and intent. The story revealed a sense of humour that was not widely known prior; multiple news outlets reported that Turing was "cheeky, funny, and really liked sex". ## Death [![](https://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Alan_Turing_Blue_Plaque_Wilmslow.jpg/250px-Alan_Turing_Blue_Plaque_Wilmslow.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_Blue_Plaque_Wilmslow.jpg) A [blue plaque](https://en.wikipedia.org/wiki/Blue_plaque "Blue plaque") on the house at 43 Adlington Road, [Wilmslow](https://en.wikipedia.org/wiki/Wilmslow "Wilmslow"), where Turing lived and died On 8 June 1954, at his house at 43 Adlington Road, [Wilmslow](https://en.wikipedia.org/wiki/Wilmslow "Wilmslow"), Turing's housekeeper found him dead. A post mortem was held that evening, which determined that he had died the previous day at age 41 with [cyanide poisoning](https://en.wikipedia.org/wiki/Cyanide_poisoning "Cyanide poisoning") cited as the cause of death. When his body was discovered, an apple lay half-eaten beside his bed, and although the apple was not tested for cyanide, it was speculated that this was the means by which Turing had consumed a fatal dose. Turing's brother, John, identified the body the following day and took the advice given by Franz Greenbaum to accept the verdict of the [inquest](https://en.wikipedia.org/wiki/Inquests_in_England_and_Wales "Inquests in England and Wales"), as there was little prospect of establishing that the death was accidental. The inquest was held the following day, which determined the cause of death to be suicide. Turing's remains were cremated at [Woking Crematorium](https://en.wikipedia.org/wiki/Woking_Crematorium "Woking Crematorium") just two days later on 12 June 1954, with just his mother, brother, and [Lyn Newman](https://en.wikipedia.org/wiki/Lyn_Irvine "Lyn Irvine") attending, and his ashes were scattered in the gardens of the crematorium, just as his father's had been. Turing's mother was on holiday in Italy at the time of his death and returned home after the inquest. She never accepted the verdict of suicide. Hodges and a later biographer, [David Leavitt](https://en.wikipedia.org/wiki/David_Leavitt "David Leavitt"), have both speculated that Turing was re-enacting a scene from the [Walt Disney](https://en.wikipedia.org/wiki/Walt_Disney "Walt Disney") film _[Snow White and the Seven Dwarfs](https://en.wikipedia.org/wiki/Snow_White_and_the_Seven_Dwarfs_\(1937_film\) "Snow White and the Seven Dwarfs (1937 film)")_ (1937), his favourite fairy tale. Both men noted that (in Leavitt's words) he took "an especially keen pleasure in the scene where the Wicked Queen immerses her apple in the poisonous brew". [![](https://upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Alan_Turing_OBE.jpg/250px-Alan_Turing_OBE.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)](https://en.wikipedia.org/wiki/File:Alan_Turing_OBE.jpg) Turing's OBE currently held in [Sherborne School](https://en.wikipedia.org/wiki/Sherborne_School "Sherborne School") archives It has also been suggested that Turing's belief in [fortune-telling](https://en.wikipedia.org/wiki/Fortune-telling "Fortune-telling") may have caused his depressed mood. As a youth, Turing had been told by a fortune-teller that he would be a genius. In mid-May 1954, shortly before his death, Turing again decided to consult a fortune-teller during a day-trip to [St Annes-on-Sea](https://en.wikipedia.org/wiki/Lytham_St_Annes "Lytham St Annes") with the Greenbaum family. According to the Greenbaums' daughter, Barbara: > But it was a lovely sunny day and Alan was in a cheerful mood and off we went ... Then he thought it would be a good idea to go to the [Pleasure Beach at Blackpool](https://en.wikipedia.org/wiki/Blackpool_Pleasure_Beach "Blackpool Pleasure Beach"). We found a fortune-teller's tent and Alan said he'd like to go in\[,\] so we waited around for him to come back ... And this sunny, cheerful visage had shrunk into a pale, shaking, horror-stricken face. Something had happened. We don't know what the fortune-teller said but he obviously was deeply unhappy. I think that was probably the last time we saw him before we heard of his suicide. ### Doubts on suicide thesis Turing's nephew, writer Dermot Turing, does not believe that his conviction or hormone treatment had anything to do with his suicide. He pointed out that the conviction ended in 1952 and the treatment the following year. Furthermore, no physiological evidence was found that the treatment had any impact on his uncle's mental health, and he had just made a list of tasks he needed to perform when he got back to his office after a public holiday. Turing may have inhaled cyanide fumes from an electroplating experiment in his spare room, and he often ate an apple before bed, leaving it half eaten. Philosopher [Jack Copeland](https://en.wikipedia.org/wiki/Jack_Copeland "Jack Copeland") has questioned various aspects of the coroner's historical verdict. He suggested an alternative explanation for the cause of Turing's death: the accidental inhalation of cyanide fumes from an apparatus used to [electroplate](https://en.wikipedia.org/wiki/Electroplating "Electroplating") gold onto spoons. The [potassium cyanide](https://en.wikipedia.org/wiki/Potassium_cyanide "Potassium cyanide") was used to [dissolve the gold](https://en.wikipedia.org/wiki/Gold#Chemistry "Gold"). Turing had such an apparatus set up in his tiny spare room. Copeland noted that the autopsy findings were more consistent with inhalation than with ingestion of the poison. Turing also habitually ate an apple before going to bed, and it was not unusual for the apple to be discarded half-eaten. Furthermore, Turing had reportedly borne his legal setbacks and hormone treatment (which had been discontinued a year previously) "with good humour" and had shown no sign of despondency before his death. He even set down a list of tasks that he intended to complete upon returning to his office after the holiday weekend. Turing's mother believed that the ingestion was accidental, resulting from her son's careless storage of laboratory chemicals. Turing biographer [Andrew Hodges](https://en.wikipedia.org/wiki/Andrew_Hodges "Andrew Hodges") theorised that Turing deliberately made his death look accidental to shield his mother from the knowledge that he had killed himself. Doubts on the suicide thesis have been also cast by [John W. Dawson Jr.](https://en.wikipedia.org/wiki/John_W._Dawson_Jr. "John W. Dawson Jr.") who, in his review of Hodges' book, recalls "Turing's vulnerable position in the Cold War political climate" and points out that "Turing was found dead by a maid, who discovered him 'lying neatly in his bed'—hardly what one would expect of "a man fighting for life against the suffocation induced by cyanide poisoning." Turing had given no hint of suicidal inclinations to his friends and had made no effort to put his affairs in order. ## Government apology and pardon Further information: [Alan Turing law](https://en.wikipedia.org/wiki/Alan_Turing_law "Alan Turing law") In August 2009, British programmer [John Graham-Cumming](https://en.wikipedia.org/wiki/John_Graham-Cumming "John Graham-Cumming") started a petition urging the British government to apologise for Turing's prosecution as a homosexual. The petition received more than 30,000 signatures. The prime minister, [Gordon Brown](https://en.wikipedia.org/wiki/Gordon_Brown "Gordon Brown"), acknowledged the petition, releasing a statement on 10 September 2009 apologising and describing the treatment of Turing as "appalling": > Thousands of people have come together to demand justice for Alan Turing and recognition of the appalling way he was treated. While Turing was dealt with under the law of the time and we can't put the clock back, his treatment was of course utterly unfair and I am pleased to have the chance to say how deeply sorry I and we all are for what happened to him ... So on behalf of the British government, and all those who live freely thanks to Alan's work I am very proud to say: we're sorry, you deserved so much better. In December 2011, William Jones and his member of Parliament, [John Leech](https://en.wikipedia.org/wiki/John_Leech_\(politician\) "John Leech (politician)"), created an [e-petition](https://en.wikipedia.org/wiki/E-petition "E-petition") requesting that the British government [pardon](https://en.wikipedia.org/wiki/Pardon "Pardon") Turing for his conviction of "gross indecency": > We ask the HM Government to grant a pardon to Alan Turing for the conviction of "gross indecency". In 1952, he was convicted of "gross indecency" with another man and was forced to undergo so-called "organo-therapy"—chemical castration. Two years later, he killed himself with cyanide, aged just 41. Alan Turing was driven to a terrible despair and early death by the nation he'd done so much to save. This remains a shame on the British government and British history. A pardon can go some way to healing this damage. It may act as an apology to many of the other gay men, not as well-known as Alan Turing, who were subjected to these laws. The petition gathered over 37,000 signatures, and was submitted to Parliament by the Manchester MP John Leech but the request was discouraged by Justice Minister [Lord McNally](https://en.wikipedia.org/wiki/Tom_McNally,_Baron_McNally#Political_career "Tom McNally, Baron McNally"), who said: > A posthumous pardon was not considered appropriate as Alan Turing was properly convicted of what at the time was a criminal offence. He would have known that his offence was against the law and that he would be prosecuted. It is tragic that Alan Turing was convicted of an offence that now seems both cruel and absurd—particularly poignant given his outstanding contribution to the war effort. However, the law at the time required a prosecution and, as such, long-standing policy has been to accept that such convictions took place and, rather than trying to alter the historical context and to put right what cannot be put right, ensure instead that we never again return to those times. John Leech, the MP for [Manchester Withington](https://en.wikipedia.org/wiki/Manchester_Withington_\(UK_Parliament_constituency\) "Manchester Withington (UK Parliament constituency)") (2005–15), submitted several bills to Parliament and led a high-profile campaign to secure the pardon. Leech made the case in the House of Commons that Turing's contribution to the war made him a national hero and that it was "ultimately just embarrassing" that the conviction still stood. Leech continued to take the bill through Parliament and campaigned for several years, gaining the public support of numerous leading scientists, including the physicist [Stephen Hawking](https://en.wikipedia.org/wiki/Stephen_Hawking "Stephen Hawking"). On 26 July 2012, a bill was introduced in the [House of Lords](https://en.wikipedia.org/wiki/British_House_of_Lords "British House of Lords") to grant a statutory pardon to Turing for offences under section 11 of the Criminal Law Amendment Act 1885, of which he was convicted on 31 March 1952. Late in the year in a letter to _[The Daily Telegraph](https://en.wikipedia.org/wiki/The_Daily_Telegraph "The Daily Telegraph")_, Hawking and 10 other signatories including the [Astronomer Royal](https://en.wikipedia.org/wiki/Astronomer_Royal "Astronomer Royal") [Lord Rees](https://en.wikipedia.org/wiki/Martin_Rees,_Baron_Rees_of_Ludlow "Martin Rees, Baron Rees of Ludlow"), [President of the Royal Society](https://en.wikipedia.org/wiki/List_of_presidents_of_the_Royal_Society "List of presidents of the Royal Society") Sir [Paul Nurse](https://en.wikipedia.org/wiki/Paul_Nurse "Paul Nurse"), [Lady Trumpington](https://en.wikipedia.org/wiki/Jean_Barker,_Baroness_Trumpington "Jean Barker, Baroness Trumpington") (who worked for Turing during the war) and [Lord Sharkey](https://en.wikipedia.org/wiki/John_Sharkey,_Baron_Sharkey "John Sharkey, Baron Sharkey") (the bill's sponsor) called on Prime Minister [David Cameron](https://en.wikipedia.org/wiki/David_Cameron "David Cameron") to act on the pardon request. The government indicated it would support the bill, and it passed its third reading in the House of Lords in October. At the bill's second reading in the [House of Commons](https://en.wikipedia.org/wiki/House_of_Commons_of_the_United_Kingdom "House of Commons of the United Kingdom") on 29 November 2013, Conservative MP [Christopher Chope](https://en.wikipedia.org/wiki/Christopher_Chope "Christopher Chope") objected to the bill, delaying its passage. The bill was due to return to the House of Commons on 28 February 2014, but before the bill could be debated in the House of Commons, the government elected to proceed under the [royal prerogative of mercy](https://en.wikipedia.org/wiki/Royal_prerogative_of_mercy "Royal prerogative of mercy"). On 24 December 2013, [Queen Elizabeth II](https://en.wikipedia.org/wiki/Queen_Elizabeth_II "Queen Elizabeth II") signed a [pardon](https://en.wikipedia.org/wiki/Royal_prerogative_of_mercy "Royal prerogative of mercy") for Turing's conviction for "gross indecency", with immediate effect. Announcing the pardon, Lord Chancellor [Chris Grayling](https://en.wikipedia.org/wiki/Chris_Grayling "Chris Grayling") said Turing deserved to be "remembered and recognised for his fantastic contribution to the war effort" and not for his later criminal conviction. The Queen pronounced Turing pardoned in August 2014. It was only the fourth royal pardon granted since the conclusion of the Second World War. Pardons are normally granted only when the person is technically innocent, and a request has been made by the family or other interested party; neither condition was met in regard to Turing's conviction. In September 2016, the government announced its intention to expand this retroactive exoneration to other men convicted of similar historical indecency offences, in what was described as an "[Alan Turing law](https://en.wikipedia.org/wiki/Alan_Turing_law "Alan Turing law")". The Alan Turing law is now an informal term for the law in the United Kingdom, contained in the [Policing and Crime Act 2017](https://en.wikipedia.org/wiki/Policing_and_Crime_Act_2017 "Policing and Crime Act 2017"), which serves as an [amnesty law](https://en.wikipedia.org/wiki/Amnesty_law "Amnesty law") to retroactively pardon men who were cautioned or convicted under historical legislation that outlawed homosexual acts. The law applies in England and Wales. Due to his repeated attempts to bring attention to the issue, Leech is now regularly described as the "architect" of Turing's pardon and subsequently the Alan Turing Law, which went on to secure pardons for 75,000 other men and women. At the British premiere of a film based on Turing's life, _[The Imitation Game](https://en.wikipedia.org/wiki/The_Imitation_Game "The Imitation Game")_, the producers thanked Leech for bringing the topic to public attention and securing Turing's pardon. On 19 July 2023, following [an apology to LGBT veterans](https://en.wikipedia.org/wiki/Sexual_orientation_and_the_military_of_the_United_Kingdom#Official_apology_to_veterans "Sexual orientation and the military of the United Kingdom") from the UK Government, [Defence Secretary](https://en.wikipedia.org/wiki/Secretary_of_State_for_Defence "Secretary of State for Defence") [Ben Wallace](https://en.wikipedia.org/wiki/Ben_Wallace_\(politician\) "Ben Wallace (politician)") suggested Turing should be honoured with a permanent statue on the [fourth plinth of Trafalgar Square](https://en.wikipedia.org/wiki/Fourth_plinth#Proposals_for_permanent_statues "Fourth plinth"), describing Turing as "probably the greatest war hero, in my book, of the Second World War, \[whose\] achievements shortened the war, saved thousands of lives, helped defeat the Nazis. And his story is a sad story of a society and how it treated him." ## Further reading ### Articles - [Copeland, B. Jack](https://en.wikipedia.org/wiki/Jack_Copeland "Jack Copeland") (ed.). ["The Mind and the Computing Machine: Alan Turing and others"](http://www.rutherfordjournal.org/article010111.html). _[The Rutherford Journal](https://en.wikipedia.org/wiki/The_Rutherford_Journal "The Rutherford Journal")_. [Archived](https://web.archive.org/web/20120318165042/http://www.rutherfordjournal.org/article010111.html) from the original on 18 March 2012. Retrieved 6 April 2009. - Copeland, B. Jack (ed.). ["Alan Turing: Father of the Modern Computer"](http://www.rutherfordjournal.org/article040101.html). _[The Rutherford Journal](https://en.wikipedia.org/wiki/The_Rutherford_Journal "The Rutherford Journal")_. [Archived](https://web.archive.org/web/20220124221719/http://rutherfordjournal.org/article040101.html) from the original on 24 January 2022. Retrieved 19 November 2013. - Hodges, Andrew (2004). "Turing, Alan Mathison". _[Oxford Dictionary of National Biography](https://en.wikipedia.org/wiki/Dictionary_of_National_Biography#Oxford_Dictionary_of_National_Biography "Dictionary of National Biography")_ (online ed.). Oxford University Press. [doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.1093/ref:odnb/36578](https://doi.org/10.1093%2Fref%3Aodnb%2F36578). (Subscription, [Wikipedia Library](https://wikipedialibrary.wmflabs.org/partners/88/) access or [UK public library membership](https://www.oxforddnb.com/help/subscribe#public) required.) - Hodges, Andrew (2007). ["Alan Turing"](http://plato.stanford.edu/entries/turing/). In Edward N. Zalta (ed.). _[Stanford Encyclopedia of Philosophy](https://en.wikipedia.org/wiki/Stanford_Encyclopedia_of_Philosophy "Stanford Encyclopedia of Philosophy")_ (Winter 2009 ed.). [Stanford University](https://en.wikipedia.org/wiki/Stanford_University "Stanford University"). Retrieved 10 January 2011. - Gray, Paul (29 March 1999). ["Computer Scientist: Alan Turing"](https://web.archive.org/web/20071016225903/http://www.time.com/time/magazine/article/0,9171,990624,00.html). _Time_. Archived from [the original](http://www.time.com/time/magazine/article/0,9171,990624,00.html) on 16 October 2007. - O'Connell, H; Fitzgerald, M (2003). "Did Alan Turing have Asperger's syndrome?". _Irish Journal of Psychological Medicine_. **20** (1). Irish Institute of Psychological Medicine: 28–31\. [doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.1017/s0790966700007503](https://doi.org/10.1017%2Fs0790966700007503). [ISSN](https://en.wikipedia.org/wiki/ISSN_\(identifier\) "ISSN (identifier)") [0790-9667](https://search.worldcat.org/issn/0790-9667). [PMID](https://en.wikipedia.org/wiki/PMID_\(identifier\) "PMID (identifier)") [30440230](https://pubmed.ncbi.nlm.nih.gov/30440230). [S2CID](https://en.wikipedia.org/wiki/S2CID_\(identifier\) "S2CID (identifier)") [53563123](https://api.semanticscholar.org/CorpusID:53563123). - O'Connor, John J.; [Robertson, Edmund F.](https://en.wikipedia.org/wiki/Edmund_F._Robertson "Edmund F. Robertson") ["Alan Mathison Turing"](https://mathshistory.st-andrews.ac.uk/Biographies/Turing.html). _[MacTutor History of Mathematics Archive](https://en.wikipedia.org/wiki/MacTutor_History_of_Mathematics_Archive "MacTutor History of Mathematics Archive")_. [University of St Andrews](https://en.wikipedia.org/wiki/University_of_St_Andrews "University of St Andrews"). ### Books - Agar, Jon (2001). _Turing and the Universal Machine_. Duxford: Icon. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-84046-250-0](https://en.wikipedia.org/wiki/Special:BookSources/978-1-84046-250-0 "Special:BookSources/978-1-84046-250-0"). - Agar, Jon (2003). _The government machine: a revolutionary history of the computer_. Cambridge, Massachusetts: MIT Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-262-01202-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-262-01202-7 "Special:BookSources/978-0-262-01202-7"). - [Babbage, Charles](https://en.wikipedia.org/wiki/Charles_Babbage "Charles Babbage") (2016) \[1864\]. Campbell-Kelly, Martin (ed.). _The Works of Charles Babbage: Passages from the Life of a Philosopher_. Oxford: Routledge. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-138-76370-8](https://en.wikipedia.org/wiki/Special:BookSources/978-1-138-76370-8 "Special:BookSources/978-1-138-76370-8"). - [Beniger, James](https://en.wikipedia.org/wiki/James_R._Beniger "James R. Beniger") (1986). [_The control revolution: technological and economic origins of the information society_](https://en.wikipedia.org/wiki/The_control_revolution:_technological_and_economic_origins_of_the_information_society "The control revolution: technological and economic origins of the information society"). Cambridge, Massachusetts: Harvard University Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-674-16986-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-674-16986-9 "Special:BookSources/978-0-674-16986-9"). - Bernhardt, Chris (2017). _Turing's Vision: The Birth of Computer Science_. MIT Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-262-53351-5](https://en.wikipedia.org/wiki/Special:BookSources/978-0-262-53351-5 "Special:BookSources/978-0-262-53351-5"). - [Bodanis, David](https://en.wikipedia.org/wiki/David_Bodanis "David Bodanis") (2005). _Electric Universe: How Electricity Switched on the Modern World_. New York: Three Rivers Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-307-33598-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-307-33598-2 "Special:BookSources/978-0-307-33598-2"). [OCLC](https://en.wikipedia.org/wiki/OCLC_\(identifier\) "OCLC (identifier)") [61684223](https://search.worldcat.org/oclc/61684223). - Bruderer, Herbert (2012). "Die Maschinen von Charles Babbage, Alan Turing und John von Neumann". _Konrad Zuse und die Schweiz. Wer hat den Computer erfunden?_ (in German). München: Oldenbourg Wissenschaftsverlag. [doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.1524/9783486716658](https://doi.org/10.1524%2F9783486716658). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-3-486-71366-4](https://en.wikipedia.org/wiki/Special:BookSources/978-3-486-71366-4 "Special:BookSources/978-3-486-71366-4"). - [Campbell-Kelly, Martin](https://en.wikipedia.org/wiki/Martin_Campbell-Kelly "Martin Campbell-Kelly"); Aspray, William (1996). [_Computer: A History of the Information Machine_](https://archive.org/details/computerhistoryo00camp). New York: Basic Books. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-465-02989-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-465-02989-1 "Special:BookSources/978-0-465-02989-1"). - [Ceruzzi, Paul E.](https://en.wikipedia.org/wiki/Paul_E._Ceruzzi "Paul E. Ceruzzi") (1998). _A History of Modern Computing_. Cambridge, Massachusetts, and London: MIT Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-262-53169-6](https://en.wikipedia.org/wiki/Special:BookSources/978-0-262-53169-6 "Special:BookSources/978-0-262-53169-6"). - [Chandler, Alfred](https://en.wikipedia.org/wiki/Alfred_D._Chandler_Jr. "Alfred D. Chandler Jr.") (1977). [_The Visible Hand: The Managerial Revolution in American Business_](https://archive.org/details/visiblehandmanag00chan). Cambridge, Massachusetts: Belknap Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-674-94052-9](https://en.wikipedia.org/wiki/Special:BookSources/978-0-674-94052-9 "Special:BookSources/978-0-674-94052-9"). - Cooper, S. Barry; van Leeuwen, Jan (2013). _Alan Turing: His Work and Impact_. New York: Elsevier. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-12-386980-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-12-386980-7 "Special:BookSources/978-0-12-386980-7"). - [Copeland, B. Jack](https://en.wikipedia.org/wiki/Jack_Copeland "Jack Copeland"), ed. (2005). [_Alan Turing's Automatic Computing Engine_](https://archive.org/details/alanturingsautom0000unse). Oxford: Oxford University Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-19-856593-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-19-856593-2 "Special:BookSources/978-0-19-856593-2"). [OCLC](https://en.wikipedia.org/wiki/OCLC_\(identifier\) "OCLC (identifier)") [224640979](https://search.worldcat.org/oclc/224640979). - Copeland, B. Jack; [Bowen, Jonathan P.](https://en.wikipedia.org/wiki/Jonathan_Bowen "Jonathan Bowen"); [Wilson, Robin](https://en.wikipedia.org/wiki/Robin_Wilson_\(mathematician\) "Robin Wilson (mathematician)"); Sprevak, Mark (2017). [_The Turing Guide_](https://en.wikipedia.org/wiki/The_Turing_Guide "The Turing Guide"). [Oxford University Press](https://en.wikipedia.org/wiki/Oxford_University_Press "Oxford University Press"). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-19-874783-3](https://en.wikipedia.org/wiki/Special:BookSources/978-0-19-874783-3 "Special:BookSources/978-0-19-874783-3"). - [Dyson, George](https://en.wikipedia.org/wiki/George_Dyson_\(science_historian\) "George Dyson (science historian)") (2012). _Turing's Cathedral: The Origins of the Digital Universe_. Vintage. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-4000-7599-7](https://en.wikipedia.org/wiki/Special:BookSources/978-1-4000-7599-7 "Special:BookSources/978-1-4000-7599-7"). - Edwards, Paul N (1996). _The closed world: computers and the politics of discourse in Cold War America_. Cambridge, Massachusetts: MIT Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-262-55028-4](https://en.wikipedia.org/wiki/Special:BookSources/978-0-262-55028-4 "Special:BookSources/978-0-262-55028-4"). - [Gleick, James](https://en.wikipedia.org/wiki/James_Gleick "James Gleick") (2011). [_The Information: A History, a Theory, a Flood_](https://en.wikipedia.org/wiki/The_Information:_A_History,_a_Theory,_a_Flood "The Information: A History, a Theory, a Flood"). New York: Pantheon. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-375-42372-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-375-42372-7 "Special:BookSources/978-0-375-42372-7"). - [Hochhuth, Rolf](https://en.wikipedia.org/wiki/Rolf_Hochhuth "Rolf Hochhuth") (1988). _Alan Turing: en berättelse_. Symposion. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-91-7868-109-9](https://en.wikipedia.org/wiki/Special:BookSources/978-91-7868-109-9 "Special:BookSources/978-91-7868-109-9"). - [Levin, Janna](https://en.wikipedia.org/wiki/Janna_Levin "Janna Levin") (2006). _A Madman Dreams of Turing Machines_. New York: Knopf. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-4000-3240-2](https://en.wikipedia.org/wiki/Special:BookSources/978-1-4000-3240-2 "Special:BookSources/978-1-4000-3240-2"). - Lubar, Steven (1993). [_Infoculture_](https://archive.org/details/infoculturesmith00luba). Boston, Massachusetts and New York: Houghton Mifflin. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-395-57042-5](https://en.wikipedia.org/wiki/Special:BookSources/978-0-395-57042-5 "Special:BookSources/978-0-395-57042-5"). - Petzold, Charles (2008). _[The Annotated Turing](https://en.wikipedia.org/wiki/The_Annotated_Turing "The Annotated Turing"): A Guided Tour through Alan Turing's Historic Paper on Computability and the Turing Machine_. [Indianapolis](https://en.wikipedia.org/wiki/Indianapolis "Indianapolis"): Wiley Publishing. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-470-22905-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-470-22905-7 "Special:BookSources/978-0-470-22905-7"). - [Smith, Michael](https://en.wikipedia.org/wiki/Michael_Smith_\(newspaper_reporter\) "Michael Smith (newspaper reporter)") (1998). _The Secrets of Station X: How the Bletchley Park codebreakers helped win the war_. [Boxtree](https://en.wikipedia.org/wiki/Macmillan_Publishers "Macmillan Publishers"). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0752221892](https://en.wikipedia.org/wiki/Special:BookSources/978-0752221892 "Special:BookSources/978-0752221892"). - Smith, Roger (1997). _Fontana History of the Human Sciences_. London: Fontana. - Turing, Sara Stoney (1959). _Alan M Turing_. W Heffer. Turing's mother, who survived him by many years, wrote this 157-page biography of her son, glorifying his life. It was published in 1959, and so could not cover his war work. Scarcely 300 copies were sold (Sara Turing to Lyn Newman, 1967, Library of [St John's College, Cambridge](https://en.wikipedia.org/wiki/St_John's_College,_Cambridge "St John's College, Cambridge")). The six-page foreword by [Lyn Irvine](https://en.wikipedia.org/wiki/Lyn_Irvine "Lyn Irvine") includes reminiscences and is more frequently quoted. It was re-published by Cambridge University Press in 2012, to honour the centenary of his birth, and included a new foreword by [Martin Davis](https://en.wikipedia.org/wiki/Martin_Davis_\(mathematician\) "Martin Davis (mathematician)"), as well as a never-before-published memoir by Turing's older brother John F. Turing. - Turing, Sara (2012). _Alan M. Turing_. [Cambridge University Press](https://en.wikipedia.org/wiki/Cambridge_University_Press "Cambridge University Press"). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-107-02058-0](https://en.wikipedia.org/wiki/Special:BookSources/978-1-107-02058-0 "Special:BookSources/978-1-107-02058-0"). (originally published in 1959 by W. Heffer & Sons, Ltd) - Weizenbaum, Joseph (1976). _Computer Power and Human Reason_. London: W.H. Freeman. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [0-7167-0463-3](https://en.wikipedia.org/wiki/Special:BookSources/0-7167-0463-3 "Special:BookSources/0-7167-0463-3"). - [Whitemore, Hugh](https://en.wikipedia.org/wiki/Hugh_Whitemore "Hugh Whitemore"); [Hodges, Andrew](https://en.wikipedia.org/wiki/Andrew_Hodges "Andrew Hodges") (1988). _Breaking the code_. S. French. This 1986 Hugh Whitemore play tells the story of Turing's life and death. In the original West End and Broadway runs, [Derek Jacobi](https://en.wikipedia.org/wiki/Derek_Jacobi "Derek Jacobi") played Turing and he recreated the role in a 1997 television film based on the play made jointly by the BBC and [WGBH, Boston](https://en.wikipedia.org/wiki/WGBH-TV "WGBH-TV"). The play is published by Amber Lane Press, [Oxford](https://en.wikipedia.org/wiki/Oxford "Oxford"), ASIN: B000B7TM0Q - Williams, Michael R. (1985). _A History of Computing Technology_. [Englewood Cliffs, New Jersey](https://en.wikipedia.org/wiki/Englewood_Cliffs,_New_Jersey "Englewood Cliffs, New Jersey"): [Prentice-Hall](https://en.wikipedia.org/wiki/Prentice-Hall "Prentice-Hall"). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [0-8186-7739-2](https://en.wikipedia.org/wiki/Special:BookSources/0-8186-7739-2 "Special:BookSources/0-8186-7739-2"). - Yates, David M. (1997). _Turing's Legacy: A history of computing at the National Physical Laboratory 1945–1995_. London: [London Science Museum](https://en.wikipedia.org/wiki/Science_Museum,_London "Science Museum, London"). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-901805-94-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-901805-94-2 "Special:BookSources/978-0-901805-94-2"). [OCLC](https://en.wikipedia.org/wiki/OCLC_\(identifier\) "OCLC (identifier)") [123794619](https://search.worldcat.org/oclc/123794619). ## See also - [Legacy of Alan Turing](https://en.wikipedia.org/wiki/Legacy_of_Alan_Turing "Legacy of Alan Turing") - [List of things named after Alan Turing](https://en.wikipedia.org/wiki/List_of_things_named_after_Alan_Turing "List of things named after Alan Turing") - [List of suicides of LGBTQ people](https://en.wikipedia.org/wiki/List_of_suicides_of_LGBTQ_people "List of suicides of LGBTQ people") - [List of pioneers in computer science](https://en.wikipedia.org/wiki/List_of_pioneers_in_computer_science "List of pioneers in computer science") - [Peter Hogg](https://en.wikipedia.org/wiki/Peter_Hogg_\(Shiburnian\) "Peter Hogg (Shiburnian)"), Turing's friend from Sherborne ### Works cited - Alexander, C. Hugh O'D. ["Cryptographic History of Work on the German Naval Enigma"](http://www.ellsbury.com/gne/gne-000.htm). The National Archives, Kew, Reference HW 25/1. [Archived](https://web.archive.org/web/20220217145825/http://www.ellsbury.com/gne/gne-000.htm) from the original on 17 February 2022. Retrieved 15 November 2010. - Beavers, Anthony (2013). ["Alan Turing: Mathematical Mechanist"](https://books.google.com/books?id=C9WQbm4ovFoC&pg=PA481). In Cooper, S. Barry; van Leeuwen, Jan (eds.). _Alan Turing: His Work and Impact_. Waltham: Elsevier. pp. 481–485\. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-12-386980-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-12-386980-7 "Special:BookSources/978-0-12-386980-7"). - [Church, Alonzo](https://en.wikipedia.org/wiki/Alonzo_Church "Alonzo Church") (1936). ["An Unsolvable Problem of Elementary Number Theory"](https://archive.org/details/sim_american-journal-of-mathematics_1936-04_58_2/page/344). _[American Journal of Mathematics](https://en.wikipedia.org/wiki/American_Journal_of_Mathematics "American Journal of Mathematics")_. **58** (2): 345–363\. [doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.2307/2371045](https://doi.org/10.2307%2F2371045). [ISSN](https://en.wikipedia.org/wiki/ISSN_\(identifier\) "ISSN (identifier)") [0002-9327](https://search.worldcat.org/issn/0002-9327). [JSTOR](https://en.wikipedia.org/wiki/JSTOR_\(identifier\) "JSTOR (identifier)") [2371045](https://www.jstor.org/stable/2371045). - [Copeland, B. Jack](https://en.wikipedia.org/wiki/Jack_Copeland "Jack Copeland") (2004a). "Colossus: Its Origins and Originators". _[IEEE Annals of the History of Computing](https://en.wikipedia.org/wiki/IEEE_Annals_of_the_History_of_Computing "IEEE Annals of the History of Computing")_. **26** (4): 38–45\. [Bibcode](https://en.wikipedia.org/wiki/Bibcode_\(identifier\) "Bibcode (identifier)"):[2004IAHC...26d..38C](https://ui.adsabs.harvard.edu/abs/2004IAHC...26d..38C). [doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.1109/MAHC.2004.26](https://doi.org/10.1109%2FMAHC.2004.26). [S2CID](https://en.wikipedia.org/wiki/S2CID_\(identifier\) "S2CID (identifier)") [20209254](https://api.semanticscholar.org/CorpusID:20209254). - Copeland, B. Jack, ed. (2004b). _The Essential Turing_. Oxford: Oxford University Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-19-825079-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-19-825079-1 "Special:BookSources/978-0-19-825079-1"). [OCLC](https://en.wikipedia.org/wiki/OCLC_\(identifier\) "OCLC (identifier)") [156728127](https://search.worldcat.org/oclc/156728127). - Copeland, B. Jack (2006). _Colossus: The secrets of Bletchley Park's code-breaking computers_. Oxford University Press. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-19-284055-4](https://en.wikipedia.org/wiki/Special:BookSources/978-0-19-284055-4 "Special:BookSources/978-0-19-284055-4"). - [Hilton, Peter](https://en.wikipedia.org/wiki/Peter_Hilton "Peter Hilton") (2006). "Living with Fish: Breaking Tunny in the Newmanry and Testery". _Colussus_. in [Copeland 2006](https://en.wikipedia.org/wiki/Alan_Turing#CITEREFCopeland2006), pp. 189–203 - Gannon, Paul (2007) \[2006\]. _Colossus: Bletchley Park's Greatest Secret_. London: Atlantic Books. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-84354-331-2](https://en.wikipedia.org/wiki/Special:BookSources/978-1-84354-331-2 "Special:BookSources/978-1-84354-331-2"). - [Hodges, Andrew](https://en.wikipedia.org/wiki/Andrew_Hodges "Andrew Hodges") (1983). [_Alan Turing: The Enigma_](https://en.wikipedia.org/wiki/Alan_Turing:_The_Enigma "Alan Turing: The Enigma"). London: Burnett Books Ltd. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-09-152130-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-09-152130-1 "Special:BookSources/978-0-09-152130-1").; basis of the film _[The Imitation Game](https://en.wikipedia.org/wiki/The_Imitation_Game "The Imitation Game")_ - [Hodges, Andrew](https://en.wikipedia.org/wiki/Andrew_Hodges "Andrew Hodges") (2012). _Alan Turing: The Enigma_. Vintage. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-09-911641-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-09-911641-7 "Special:BookSources/978-0-09-911641-7"). - [Leavitt, David](https://en.wikipedia.org/wiki/David_Leavitt "David Leavitt") (2007). _The man who knew too much: Alan Turing and the invention of the computer_. Phoenix. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-7538-2200-5](https://en.wikipedia.org/wiki/Special:BookSources/978-0-7538-2200-5 "Special:BookSources/978-0-7538-2200-5"). - [Lewin, Ronald](https://en.wikipedia.org/wiki/Ronald_Lewin "Ronald Lewin") (1978). _Ultra Goes to War: The Secret Story_. Classic Military History (Classic Penguin ed.). London: Hutchinson & Co (published 2001). [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-1-56649-231-7](https://en.wikipedia.org/wiki/Special:BookSources/978-1-56649-231-7 "Special:BookSources/978-1-56649-231-7"). - [Mahon, A. P.](https://en.wikipedia.org/wiki/A._P._Mahon "A. P. Mahon") (June 1945). [_The History of Hut Eight, 1939 - 1945_](https://web.archive.org/web/20070220023304/http://www.ellsbury.com/hut8/hut8-000.htm). [National Archives, Kew](https://en.wikipedia.org/wiki/National_Archives,_Kew "National Archives, Kew"): United Kingdom. Archived from [the original](http://www.ellsbury.com/hut8/hut8-000.htm) on 20 February 2007. Retrieved 10 December 2009 – via ellsbury.com. Reference HW 25/2 In 1996, a copy was released to the [National Archives and Records Administration](https://en.wikipedia.org/wiki/National_Archives_and_Records_Administration "National Archives and Records Administration"). Then a copy was released to [National Archives, Kew](https://en.wikipedia.org/wiki/National_Archives,_Kew "National Archives, Kew"). Mahon's account is first-hand from October 1941. Also published as a book chapter ([doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.1093/oso/9780198250791.003.0010](https://doi.org/10.1093%2Foso%2F9780198250791.003.0010)), and a volume in a series. - [Oakley, Brian](https://en.wikipedia.org/wiki/Brian_Oakley "Brian Oakley"), ed. (2006). _The Bletchley Park War Diaries: July 1939 – August 1945_ (2.6 ed.). Wynne Press. - Sipser, Michael (2006). _Introduction to the Theory of Computation_. PWS Publishing. [ISBN](https://en.wikipedia.org/wiki/ISBN_\(identifier\) "ISBN (identifier)") [978-0-534-95097-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-534-95097-2 "Special:BookSources/978-0-534-95097-2"). - Turing, A. M. (1937) \[Delivered to the Society November 1936\]. ["On Computable Numbers, with an Application to the Entscheidungsproblem"](http://www.comlab.ox.ac.uk/activities/ieg/e-library/sources/tp2-ie.pdf) (PDF). _Proceedings of the London Mathematical Society_. 2. Vol. 42, no. 1\. pp. 230–65\. [doi](https://en.wikipedia.org/wiki/Doi_\(identifier\) "Doi (identifier)"):[10.1112/plms/s2-42.1.230](https://doi.org/10.1112%2Fplms%2Fs2-42.1.230). [Archived](https://web.archive.org/web/20110506090827/http://www.comlab.ox.ac.uk/activities/ieg/e-library/sources/tp2-ie.pdf) (PDF) from the original on 6 May 2011. Retrieved 15 July 2009. ## Notes ## References ## External links - [Alan Turing](https://www.newscientist.com/people/alan-turing/) archive on [New Scientist](https://en.wikipedia.org/wiki/New_Scientist "New Scientist") - [Alan Turing plaques](https://openplaques.org/people/368) [Archived](https://web.archive.org/web/20240424201739/http://openplaques.org/people/368) 24 April 2024 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") on _openplaques.org_ **Papers** - [Alan Turing Papers](https://archiveshub.jisc.ac.uk/manchesteruniversity/data/gb133-tur/add) – [University of Manchester Library](https://en.wikipedia.org/wiki/University_of_Manchester_Library "University of Manchester Library") - [Science in the Making](https://makingscience.royalsociety.org/s/rs/people/fst00117605)[Archived](https://web.archive.org/web/20230404044604/https://makingscience.royalsociety.org/s/rs/people/fst00117605) 4 April 2023 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") Alan Turing's papers in the [Royal Society](https://en.wikipedia.org/wiki/Royal_Society "Royal Society")'s archives - [The Turing Digital Archive](https://turingarchive.kings.cam.ac.uk/) – contains scans of some unpublished documents and material – [King's College, Cambridge](https://en.wikipedia.org/wiki/King's_College,_Cambridge "King's College, Cambridge") - "[Pryce’s Buoy](https://doi.org/10.1093/res/hgag047)", autofiction. Transcribed by Sarah Dillon. _The Review of English Studies_, 2026. **Interviews** - [Oral history interview with Nicholas C. Metropolis](http://purl.umn.edu/107493), [Charles Babbage Institute](https://en.wikipedia.org/wiki/Charles_Babbage_Institute "Charles Babbage Institute"), University of Minnesota. Metropolis was the first director of computing services at [Los Alamos National Laboratory](https://en.wikipedia.org/wiki/Los_Alamos_National_Laboratory "Los Alamos National Laboratory"); topics include the relationship between Turing and [John von Neumann](https://en.wikipedia.org/wiki/John_von_Neumann "John von Neumann") **Articles** - [How Alan Turing Cracked The Enigma Code](http://www.iwm.org.uk/history/how-alan-turing-cracked-the-enigma-code) Imperial War Museums - Jones, G. James (11 December 2001). ["Alan Turing – Towards a Digital Mind: Part 1"](https://web.archive.org/web/20070803163318/http://www.systemtoolbox.com/article.php?history_id=3). _System Toolbox_. The Binary Freedom Project. Archived from [the original](http://www.systemtoolbox.com/article.php?history_id=3) on 3 August 2007. **Websites** - [AlanTuring.net](https://web.archive.org/web/20181012014022/http://www.alanturing.net/) – Turing Archive for the History of Computing by [Jack Copeland](https://en.wikipedia.org/wiki/Jack_Copeland "Jack Copeland") - [Alan Turing](http://www.turing.org.uk/) site maintained by [Andrew Hodges](https://en.wikipedia.org/wiki/Andrew_Hodges "Andrew Hodges") including a [short biography](https://web.archive.org/web/20180721235734/http://www.turing.org.uk/bio/part1.html) **Events** - [CiE 2012: Turing Centenary Conference](http://cie2012.eu/) - [Alan Turing Year](http://www.mathcomp.leeds.ac.uk/turing2012/) [Archived](https://web.archive.org/web/20190217215512/http://www.mathcomp.leeds.ac.uk/turing2012/) 17 February 2019 at the [Wayback Machine](https://en.wikipedia.org/wiki/Wayback_Machine "Wayback Machine") **Sherborne School** - [Sherborne School Archives](https://web.archive.org/web/20160104203150/http://oldshirburnian.org.uk/wp-content/uploads/2015/09/TURING-Alan-Mathison.pdf) – holds papers relating to Turing's time at Sherborne School - [Alan Turing and the 'Nature of Spirit'](https://oldshirburnian.org.uk/alan-turing-and-the-nature-of-spirit/) (Old Shirburnian Society) - [Alan Turing OBE, PhD, FRS (1912–1954)](https://oldshirburnian.org.uk/alan-turing/) (Old Shirburnian Society)