Who was Alan Turing
Alan Mathison Turing (1912–1954) was a British mathematician and cryptanalyst whose work encompassed computation and machine intelligence. He worked at Bletchley Park during the Second World War and spent the final stage of his career in Manchester. [3]
Education: Sherborne and Cambridge
He was born in London on 23 June 1912. School letters preserved at King’s College reveal interests in mathematics, chemistry and inventions. He attended Hazelhurst and Sherborne, and as a teenager prepared an account of Einstein’s relativity for his mother. These documents provide evidence of his education beyond familiar anecdotes about his talent. [1]
In 1931 he entered King’s College, Cambridge, on a mathematics scholarship. He graduated with distinction in 1934 and received a fellowship in 1935. This placed him within mathematical research before his career expanded into cryptography, computers and biology. [2]
Doctoral research at Princeton
From 1936 to 1938 he studied at Princeton under Alonzo Church. A revised version of his thesis, Systems of Logic Based on Ordinals, appeared in 1939. The university archives preserve correspondence with Church, documenting a scientific relationship that continued after his return to Cambridge. [5]
The mathematics department’s assessment of 16 May 1938 praised both his technical ability and his understanding of relationships between problems. It also identified contributions to mathematical analysis. His doctorate was more than an extension of a machine design: it belonged to a broader investigation of logic and foundations. [24]
The universal machine and computation
In On Computable Numbers, written in 1936, he described a model that reads symbols on a tape and follows instructions to operate on them. The universal machine was a mathematical construction, preceding electronic computers that implemented programming ideas. It examined what a calculation procedure could do independently of a particular physical device. [11]
Bletchley Park and naval Enigma
He joined the Government Code and Cypher School in September 1939. He led Hut 8’s work on German naval Enigma and worked closely with Joan Clarke. Exchanges with Polish cryptanalysts formed part of this collective history: British advances also built on earlier contributions from other teams. [9]
The Bombe mechanised the search for possible settings using fragments of expected message text. The first machine began operating in March 1940. It formed one stage in an extensive chain of interception, analysis and checking involving many people; it was not a general-purpose computer. [7]
Gordon Welchman added the diagonal board, a major improvement to the design. This contribution explains the name Turing-Welchman Bombe and illustrates why the entire cryptanalytic process cannot be attributed to one person. [8]
Statistical cryptanalysis
Banburismus used statistical analysis to reduce possible Enigma wheel arrangements. Turing also developed Turingery for the Lorenz cipher, distinct from the Bombe and the construction of Colossus. These methods extended his work beyond a single machine. He received the OBE in 1946 for his wartime service. [25]
Delilah: protecting voice communications
At Hanslope Park he worked with Donald Bayley on Delilah, a portable system for encrypting voice communications. Surviving notebooks document development between 1943 and 1945. A recording was used to demonstrate it after the war. This project reveals another aspect of his cryptographic work: designing protection as well as analysing other systems. [10]
ACE: from design to computer
Turing joined the National Physical Laboratory in 1945 and presented plans for the Automatic Computing Engine in 1946. He remained associated with the project until leaving in 1948, following leave in Cambridge. The work connected logical research with practical decisions about building and programming an electronic computer. [6]
Jim Wilkinson, who had worked with Turing on the logical design, led the team that built Pilot ACE. His work included matrix calculations and numerical analysis. [23] The smaller version was completed in 1950, after Turing had moved to Manchester. The original design, the team’s implementation and subsequent applications represent different stages of its history. [22]
Manchester, programming and archives
The University of Manchester collection preserves Turing’s Mark I programming manual alongside notes on computing and morphogenesis. It also contains correspondence with researchers including Christopher Strachey, Robin Gandy and Maurice Wilkes. These materials document programming and scientific discussion alongside his better-known theoretical work. [14]
Machine intelligence and the imitation game
In Computing Machinery and Intelligence (1950), he replaced an abstract debate about thinking with a written question-and-answer game involving a machine. He also explored programs that learn through education and experience. The discussion concerns behaviour and learning; it does not establish a test of consciousness or a certification of reliability. [12]
Public discussion of computers
The research also reached radio audiences. King’s preserves scripts of a BBC Third Programme discussion broadcast in January 1952 with Turing, Max Newman, Geoffrey Jefferson and Richard Braithwaite. Whether machines could think was being debated across mathematics, philosophy and medicine before computing became a widespread commercial activity. [21]
Computers and games
Games also featured in his publications. Digital Computers Applied to Games was his contribution to Faster than Thought, edited by B. V. Bowden in 1953. King’s preserves the typescript with handwritten corrections, documenting his interest in computer uses beyond numerical calculation. [26]
Morphogenesis: how patterns emerge
The Chemical Basis of Morphogenesis appeared in 1952. Turing investigated how reacting and diffusing substances could generate patterns from an initially uniform state. The paper presents mathematical models of instability and proposes explanations for particular biological forms. It investigates mechanisms of formation rather than providing a complete account of every developmental process. [13]
Other mathematical publications
The London Mathematical Society catalogue records work beyond the universal machine: almost periodicity, ordinal-based logic and calculations of the Riemann zeta function. It also lists the correction to On Computable Numbers. This bibliography shows the continuity of his mathematical interests across different stages of his professional life. [18]
Persecution, death and redress
In 1952 he was convicted for a homosexual relationship under the law then in force and subjected to hormonal treatment. He lost the security clearance required to continue working with GCHQ. He received a posthumous pardon on 24 December 2013, alongside public recognition of the discriminatory treatment he had suffered. [15]
He died on 7 June 1954 and was found the following day. [22] In 2017, provisions known as Turing’s Law extended redress to other historical convictions for consensual same-sex relationships, subject to the legislation’s conditions. The individual 2013 pardon and the later measure are distinct events. [16]
Recognition and legacy
The ACM Turing Award has been presented since 1966 for lasting technical contributions, with particular emphasis on specific achievements. It can recognise essential collaborators in a shared advance. Its name connects Turing’s legacy with later research generations without attributing their discoveries to him personally. [20]
The Alan Turing Institute was established in 2015 by five British universities and the Engineering and Physical Sciences Research Council as a national data science institute; its artificial intelligence remit was clarified in 2017. [19] The Bank of England placed his portrait on the £50 note issued on 23 June 2021, alongside visual references to his mathematical work. [17]
Pilot ACE and structural failure investigations
The Science Museum records that Pilot ACE was used to analyse metal fatigue following the BOAC Flight 781 Comet accident. This is a specific application of a machine derived from Turing’s design to aviation safety investigations; the source does not attribute the personal investigation of the accident to Turing. [4]
