AP Computer Science Java AP Computer Science Principles AP Physics C++ Astronomy NetLogo Python JavaScript Robotics Using Java Electronics Independent Study The Site
Alan Turing            Quotations

Major Contribution:
Considered the father of Computer Science for his extensive contributions.

Alan Turing was an English mathematician, logician, and cryptographer. He provided an influential formalization of the concept of the algorithm and computation with the Turing machine, formulating the now widely accepted "Turing" version of the Church–Turing thesis, namely that any practical computing model has either the equivalent or a subset of the capabilities of a Turing machine. With the Turing test, he made a significant and characteristically provocative contribution to the debate regarding artificial intelligence: whether it will ever be possible to say that a machine is conscious and can think.

He later worked at the National Physical Laboratory, creating one of the first designs for a stored-program computer, although it was never actually built. In 1948 he moved to the University of Manchester to work on the Manchester Mark I, then emerging as one of the world's earliest true computers.

During the Second World War Turing worked at Bletchley Park, Britain's code breaking center, and was for a time head of Hut 8, the section responsible for German naval cryptanalysis. He devised a number of techniques for breaking German ciphers, including the method of the bombe, an electromechanical machine that could find settings for the Enigma machine. A picture of the Enigma is on the left.

His parents enrolled him at St Michael's, a day school, at the age of six. The headmistress recognized his genius early on, as did many of his subsequent educators. In 1926, at the age of 14, he went on to Sherborne School in Dorset. His first day of term coincided with General Strike in England, but so determined was he to attend his first day that he rode his bike unaccompanied more than 60 miles from Southampton to school, stopping overnight at an inn.

Turing's natural inclination toward mathematics and science did not earn him respect with the teachers at Sherborne, a famous and expensive public school, whose definition of education placed more emphasis on the classics.

His headmaster wrote to his parents: "I hope he will not fall between two schools. 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 even studied elementary
calculus. In 1928, aged 16, Turing encountered Albert Einstein's work; not only did he grasp it, but he extrapolated Einstein's questioning of Newton's laws of motion from a text in which this was never made explicit.

Turing's unwillingness to work as hard on his classical studies as on science and mathematics meant he failed to win a scholarship to Trinity College, Cambridge, and went on to the college of his second choice, King's College, Cambridge. Turing was an undergraduate at King's College from 1931 to 1934, graduating with a distinguished degree, and in 1935 was elected a fellow at King's on the strength of a dissertation on the central limit theorem.

In his momentous paper "On Computable Numbers, with an Application to the
Entscheidungsproblem" (submitted on 28 May 1936), Turing reformulated Kurt Gödel's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with what are now called Turing machines, formal and simple devices. He proved that such a machine would be capable of performing any conceivable mathematical problem if it were representable as an algorithm, even if no actual Turing machine would be likely to have practical applications, being much slower than alternatives.

Bletchley Park

Turing machines are to this day the central object of study in
theory of computation. He went on to prove that there was no solution to the Entscheidungsproblem by first showing that the halting problem for Turing machines is undecidable: it is not possible to decide, in general, algorithmically whether a given Turing machine will ever halt.

While his proof was published subsequent to
Alonzo Church's equivalent proof in respect to his lambda calculus, 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.

During the
Second World War, Turing was a main participant in the efforts at Bletchley Park to break German ciphers. Building on cryptanalysis work carried out in Poland before the war, he contributed several insights into breaking both the Enigma machine and the Lorenz SZ 40/42 (a teletype cipher attachment codenamed "Tunny" by the British), and was, for a time, head of Hut 8, the section responsible for reading German naval signals.

Within weeks of arriving at Bletchley Park, Turing had designed an electromechanical machine which could help break Enigma: the bombe, named after and building upon the original Polish-designed bomba. They were also referred to as "Bronze Goddesses" because their cases were made of bronze, but they were more prosaically described by operators as being "like great big metal bookcases". The bombe, with an enhancement suggested by mathematician Gordon Welchman, became one of the primary tools, and the major automated one, used to attack Enigma-protected message traffic.