simple:Alan Turing

*Alan Turing*

**Alan Mathison Turing** (June 23, 1912 - June 7, 1954) was a British mathematician and is considered to be one of the fathers of modern computer science. He provided an influential formalisation of the concept of algorithm and computation: the Turing machine. He formulated the now widely accepted Church-Turing thesis, namely that every other practical computing model had either the equivalent or a subset of the capabilities of a Turing machine. During World War II he headed a successful effort of breaking the German
secret code. After the war, he worked with one of the earliest digital computers, and later he provided a provocative contribution to the discussion "Can machines think?"

## Childhood and youth

He was born in Paddington to Civil Service officer Julius Mathison Turing and his wife Ethel (*née* Stoney). His father's Indian Civil Service commission was still active, and during Turing's childhood years his father travelled between England and India, leaving his family to stay with friends in England due to concerns over the dangers of the British colony. Very early in life, Turing showed signs of the genius he was to display more prominently later. He is said to have taught himself to read in three weeks, and to have shown an early affinity to numbers and puzzles.

His parents enrolled him at St. Michael's, a day school, at six years of age. The headmistress recognized his genius early on, as did many of his subsequent educators at Marlborough College (a public school). At Marlborough, he first reported having problems with bullies. He went on to the Sherborne boarding school at 13, where his first day was actually covered in the local press. There was a general strike in England, and Turing rode his bike sixty miles to school, stopping overnight at an inn.

Turing's natural inclination toward the sciences did not earn him respect with the teachers and administrators at Sherborne, whose definition of education emphasized the Classics rather than science. But despite this, Turing continued to show remarkable prowess in the studies he loved, solving advanced (for his age) problems in 1927 without having even studied elementary calculus.

In 1928, Turing discovered Albert Einstein's work, and grasped it at a mere sixteen years of age, even extrapolating Einstein's Law of Motion from a text in which it was never made explicit.

## College and his work on computability

Due to his unwillingness to work as hard on his Classical studies as on science and mathematics, Turing failed his final examinations several times, and went on to the college of his second choice, King's College, Cambridge, rather than his first choice, Trinity. He studied under G. H. Hardy, a well respected mathematician who held the Sadleirian Chair at Cambridge, then a centre for mathematical research and study. He studied as an undergraduate from 1931 - 1934. In 1935 he was elected a Fellow at King's College.

In his monumental paper "On Computable Numbers, with an Application to the Entscheidungsproblem" (1936), he reformulated Kurt Goedel's 1931 results on the limits of proof and computation, substituting Goedel's universal artihmetics-based formal language by Turing machines, formal devices capable of performing any conceivable mathematical problem once it was represented as an algorithm. Turing machines are to this day the central object of study in computational theory. He went on to prove that there was no solution to the *Entscheidungsproblem* by first showing that the halting problem for Turing machines is unsolvable: it is not possible to algorithmically decide whether a given Turing machine will ever halt. While his proof was published subsequent to that of Alonzo Church, Turing's work is considerably more accessible and intuitive. It was also novel in its notion of a "Universal (Turing) Machine", the idea that such a machine could perform the tasks of any other machine. The paper also introduces the notion of definable numbers.

Most of 1937 and 1938 he spent at Princeton University, studying under Alonzo Church. In 1938 he obtained his Ph.D from Princeton; his dissertation introduced the notion of hypercomputation where Turing machines are augmented with so-called oracles, allowing a study of problems that cannot be solved algorithmically.

Back in Cambridge in 1939, he attended lectures by Ludwig Wittgenstein about the foundations of mathematics. The two argued and disagreed vehemently, with Turing defending formalism and Wittgenstein arguing that mathematics is overvalued and does not discover any absolute truths.

## Code breaking

During the World War II he was a major participant in the code breaking efforts at Bletchley Park on cracking Nazi Enigma ciphers. He contributed several mathematical insights, both to breaking the Enigma code and the Fish teletype cyphers (machines made by both Lorenz and Siemens). The Fish insights were useful in the development of the special-purpose digital computer Colossus, which was developed by Max Newman and built at the Post Office Research Station at Dollis Hill by a team led by Thomas Flowers in 1943 and used to crack Fish cyphers. Turing also designed the "Bombe", an advanced versions of Polish Rejewski's "Bomba" machine used to assist in finding keys for Enigma messages. These were electromechanical devices coupling several "Enigma machines" which were able to eliminate at high speed large numbers of possible key settings for blocks of Enigma traffic.

Turing's work on breaking the Enigma code was kept secret until the 1970s; not even his close friends knew about it.

## Work on early computers; the Turing Test

From 1945 to 1948 he was at the National Physical Laboratory, where he worked on the design of ACE (Automatic Computing Engine). In 1949 he became Deputy Director of the computing laboratory at the University of Manchester, and worked on software for one of the earliest true computers - the Manchester Mark I. During this time he continued to do more abstract work, and in "Computing Machinery and Intelligence" (Mind, October 1950), Turing tackled the problem of artificial intelligence, and proposed an experiment now known as the Turing test, an attempt to define a standard for a machine to be called "sentient".

In 1952 Turing wrote a chess program. Lacking a computer powerful enough to execute it, he himself simulated the computer, taking about half an hour per move. One game was recorded; the program lost to a colleague of Turing.

## Persecution for homosexuality and death

Persecution of Turing for his homosexuality crippled his career. In 1952, his male lover helped an accomplice to break into Turing's house and commit larceny. Turing went to the police to report the crime. As a result of the police investigation, he was charged with "gross indecency and sexual perversion" (see sodomy law). He unapologetically offered no defence, and was convicted. Following the well-publicised trial, he was given a choice between incarceration and libido-reducing hormonal treatment. He chose the hormone injections, which lasted for a year, with side effects including the development of breasts during that period. In 1954, he died of poisoning after eating a cyanide-laced apple. Most believe that his death was intentional, and the death was ruled a suicide. His mother, however, strenuously argued that the ingestion was accidental due to his careless storage of laboratory chemicals.

## See also

- The Turing Award is given by the Association for Computing Machinery to a person for technical contributions to the computing community
- Famous gay lesbian or bisexual people

## External links