Alan Turing (1912-1954) was a brilliant mathematician and pioneer of computer science. During the Second World War, he was part of a top secret group of codebreakers who helped to break the German Enigma machine. This codebreaking work significantly helped the Allies to win the war – especially the naval war in the Atlantic. Due to the top-secret nature of his work, Turing gained little outer recognition for his work, (though he did get an OBE in 1948). In 1952, he was arrested for gross indecency and a year later died from cyanide poisoning. Posthumously Turing was granted an official public apology in 2009 and a posthumous pardon in 2013.

#### Early life

Turning was born in London on 23 June 1912. His father served in the Indian civil service, and along with his brother, John, they spent some time in Hastings, where they were brought up by a retired Army couple.

Turing was a precious student, showing exceptional talent in mathematics and science. He was bored by the classical subjects such as Latin and Greek and often pursued his own studies, such as solving mathematical problems. From the age of 13, he studied at Sherborne public school in Dorset. The first day of school coincided with the 1926 General Strike, but Turing was so keen to attend, he cycled the 60 miles to school on his own. Turing was also a good distance runner and kept up running throughout his life.

At school, his mathematical genius and eccentric ways made it difficult for him to fit in, and he was something of a loner. He made a very close friendship with a boy called Christopher Morcom. They shared an interest in maths, astronomy and science. Morcom’s death in 1930 from bovine tuberculosis hit Turing hard because he was his only close friend. During his teenage years, Turing read Albert Einstein‘s theory of relativity, and his notes display a profound understanding.

After Sherborne, Turing studied mathematics at King’s College, Cambridge (1931-34). He received first class honours, and within a year of graduating, Turing wrote a dissertation on Central Limit Theorem – which is a component of probability theory. This led him to be elected at an unusually young age to be a fellow at King’s College.

After the more narrow confines of an English public school, Cambridge was an intellectually liberating experience for Turing. He became involved in the anti-war movement of 1933 but rejected both Marxism and pacificism. He was close to liberal Cambridge intellectuals like John M Keynes and A.C. Pigou. At university, he enjoyed rowing and running. Turing was a keen runner and often was seen running along the river; he was known to run all the way to London for a meeting.

In 1936, he published another seminal paper “On Computable Numbers with an Application to the Entscheidungsproblem” (decision problem) It included the notion of a Universal machine which was a machine that would be able to solve any mathematical problem with the right algorithm. This is a central concept to modern computing.

From 1936 to 1938, he spent time in the US at Princeton studying mathematics and cryptology, obtaining his PhD Turing had an opportunity to stay in the US with John Von Neumann but chose to return to Cambridge. Back in Cambridge, he attended philosophical lectures of Ludwig Wittgenstein, with whom he debated about the philosophical importance of maths.

From September 1938, Turing began working part-time with the British codebreaking organisation (GC&CS). From July 1939, Turing became involved in searching for better ways to decode Enigma messages. Turing developed a machine (called Bomb) using crib-based decryption which sought for the rotor order and settings of Enigma. When the machine recognised a failed setting, it electronically moved on to the next combination. Turing developed a weighting of evidence, which enabled him to skip certain combinations, making it much quicker. Turing stated he used a combination of intuition and reasoning.

“Mathematical reasoning may be regarded rather schematically as the exercise of a combination of two facilities, which we may call intuition and ingenuity. The activity of the intuition consists in making spontaneous judgements which are not the result of conscious trains of reasoning.” Alan Turing, “

Systems of Logic Based on Ordinals,” section 11: The purpose of ordinal logics(1938)

The Germans believed Enigma was unbreakable because of the huge number of possible combinations (10 to the power of 19). However, by 1940, the electromechanical machine was able to intercept and decode enigma messages. He also used statistical analysis to optimise the different possibility in the code-breaking process. Turing’s work was deemed so important to national security it was classified for 70 years.

The machine was a considerable success and gave the Allies warning about German military operations. This was particularly vital for the Atlantic War, giving warnings of u-boat attacks on convoys. Despite the vital work, Turing’s team in Hut 8 at Bletchley Park felt frustrated they had insufficient resources. In October 1941, they wrote to Winston Churchill asking for more resources. Churchill immediately acted on their request, and they became much better resourced. By the end of the war, there were 200 Turing machines (bombs) in operation.

Turing had little interest in the practical aspects of running a department; he preferred to work alone, choosing the most difficult aspects of code-breaking – often aspects that others thought impossible. Hugh Alexander was the de facto leader of Turing’s Hut 8, but he was keen to reflect on Turing’s indispensable role.

“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… many of us in Hut 8 felt that the magnitude of Turing’s contribution was never fully realised by the outside world”

Even after the war, the British security services wanted to keep secret the way that supposedly impregnable code machines could be broken.

Turing had a reputation for eccentricity. He dressed shabbily without a tie, giving the impression of being permanently absorbed in his mathematical puzzles and code-breaking. He could be awkward in personal relations and blunt – especially towards those he considered charlatans or status-seekers. Amongst his colleagues, he was known as ‘Prof’, and his eccentricities included wearing his gas mask while cycling to avoid hay fever.

In 1942, Turing travelled to the US, where he became involved in pioneering attempts at the electronic enciphering of speech in telephones. Back in the UK, Turing helped to develop a portable secure voice communicator name, named Delilah. They successfully encrypted a speech of Churchill, but it was too late for use in the war.

After the war, he began work on a new generation of computers, which included the Automatic computing engine (ACE) and a design for the first stored-program computer. The full version of ACE was not built until after Turing’s death, but it was a major step-stone for the modern computer, and later pioneering computers relied on aspects of ACE’s new ideas.

In 1948, he had a trial for the British Olympic marathon team. Despite injury, he managed a time of 2 hours 44 minutes and just missed out.

In 1948, Turing moved to Manchester, where he was made deputy director of the Computing Laboratory at the University of Manchester. Here he developed software for an early computer ‘Manchester Mark I’. He also became interested in the philosophical and practical concept of artificial intelligence. Turing is considered the father of artificial intelligence as he developed a test to see whether a computer could be considered intelligent. An important work was “Computing Machinery and Intelligence.” (1950) He devised “The Imitation Game” now known as the Turing test; the test stated a computer could be considered to ‘think’ if a human could not distinguish between the reply of a computer and a human.

“The idea behind digital computers may be explained by saying that these machines are intended to carry out any operations which could be done by a human computer.”

Turing, Alan. *Computing Machinery and Intelligence* (1950)

Turing also developed one of the very first computer chess games.

In 1951, he also turned his attention to mathematical biology – fascinated with why plant structures exhibited Fibonacci numbers (every number after the first two is the sum of the two preceding ones 1,1,2,3,5,8,13)

In 1952, he was elected to a fellowship of the Royal Society.

During the war, Turing proposed to Joan Clark, a fellow mathematician at Hut 8. Clark accepted, however, the engagement was short-lived and Turing broke it off. Turing felt he was not being sincere and he admitted he was a homosexual. (which at the time was illegal in the UK)

In 1952, Turing began an affair with an unemployed man in Manchester. On 23 January, his home was burgled and the police investigated the burglary. Turing’s war record would not have been available to the police as it would have been covered by the Official Secrets Act. In the course of their investigation, Murray admitted that he and Turing were involved in a homosexual relationship. Murray was also responsible for the burglary. Turing admitted guilt and accepted the sentence of chemical castration (rather than a prison term). The drug was a form of synthetic oestrogen.

Turing lost his official clearances, though he retained his job.

On 8 June 1954, he was found dead in his rented room. An inquest returned a verdict of suicide from cyanide poisoning. It is possible that it was not suicide but accidental ingestion from an experiment of electroplating gold onto spoons.

In 2013, a bill was passed offering statutory pardon to Turing for offences under section 11 of the Criminal Law Amendment Act 1885. In 2016, the law (known as Turing’s law) was widened to retroactively pardon all men who were convicted under the historical legislation of gross indecency.

Citation: Pettinger, Tejvan. “Biography of Alan Turing”, Oxford, UK. *www.biographyonline.net* Published 18 September 2018.

### Alan Turing: The Enigma Man

Alan Turing: The Enigma Man

by Nigel Cawthorne at Amazon

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