Alan Turing, was a British mathematician, logician, crypt-analyst, philosopher, computer scientist and mathematical biologist. He provided a formalization of the concepts of “algorithm” and “computation” with the Turing machine, which can be considered a model of a general purpose computer. Turing is also considered to be the father of theoretical computer science and artificial intelligence.

During World War II, Turing worked for the Government Code and Cypher School (GC&CS) at Bletchley Park, Britain’s code-breaking center. Turing’s pivotal role in cracking intercepted coded messages enabled the Allies to defeat the Nazis in several crucial battles. After the war, he worked at the National Physical Laboratory, where he designed the ACE, among the first designs for a stored-program computer.

He was born in London but conceived in India, where his father was employed in the Indian Civil Services. As a boy, he was fascinated by chemistry, performing a wide variety of experiments, and by machinery. Turing attended Sherborne, an English boarding school. In 1931, he won a scholarship to King’s College, Cambridge. After completing his dissertation, which included a rediscovery of the Central Limit Theorem, a famous Theorem in statistics, he was elected a fellow of his college.

In 1935, Turing became fascinated with a decision problem, a problem by the great German mathematician Hilbert, which asked whether there is a general method that can be applied to any assertion to determine whether the assertion is true. Turing enjoyed running and one day, while resting after a run, he discovered the key ideas needed to solve the decision problem. In his solution, he invented what is now called a **Turing machine** as the most general model of a computing machine. Using these machines, he found a problem, involving what he called computable numbers, that could not be decided using a general method.

From 1936 to 1938 Turing visited Princeton University to work with Alonzo Church, who had also solved Hilbert’s decision problem. In 1939 Turing returned to King’s College. However, at the outbreak of World War II, he joined the Foreign Office, performing cryptanalysis of German ciphers. His contribution to the breaking of the code of the Enigma, a mechanical German cipher machine, played an important role in winning the war.

After the war, Turing worked on the development of early computers. He was interested in the ability of machines to think, proposing that if a computer could not be distinguished from a person based on written replies to questions, it should be considered to be “thinking.” He was also interested in biology, having written on morphogenesis, the development of form in organisms. In 1954 Turing committed suicide by taking cyanide, without leaving a clear explanation.