Alan Turing

Alan Turing was a British mathematician, logician, and computer scientist who is regarded as the father of theoretical computer science and artificial intelligence. His work on computation and on cryptography shaped the modern world.

Early Life and Education

Turing was born in London in 1912 and spent much of his childhood in India, where his father worked in the civil service. He was educated at Sherborne School and at King's College, Cambridge.

He took his degree in mathematics at Cambridge in 1934 and was elected a fellow of the college in 1935. He studied with Alonzo Church at Princeton University and took his doctorate there in 1938.

The Turing Machine and Computability

Turing published his paper On Computable Numbers in 1936 at the age of twenty-four. The paper introduced the abstract device that became known as the Turing machine.

The machine consists of an infinite tape and a read-write head that follows a set of rules. Turing showed that some problems cannot be solved by any such machine.

The work provided a negative answer to the decision problem posed by David Hilbert. It founded the theory of computability and anticipated the digital computer.

The Church-Turing thesis states that any function that can be computed by an effective procedure can be computed by a Turing machine. The thesis is a foundation of computer science.

The Codebreaking at Bletchley Park

During the Second World War Turing worked at the Government Code and Cypher School at Bletchley Park. He led the effort to break the German Enigma cipher.

He designed the electromechanical machine known as the Bombe, which searched for the settings of the Enigma rotors. The intelligence derived from the decrypts is believed to have shortened the war by years.

He later worked on the more complex Lorenz cipher and on the development of the Colossus computer. He travelled to the United States to share the results with the American cryptanalysts.

He was awarded the Order of the British Empire in 1946 for his war service. The work remained secret for decades and was not widely known until the 1970s.

Artificial Intelligence and the Turing Test

Turing published his paper Computing Machinery and Intelligence in 1950. The paper proposed the test that became known as the Turing test.

The test asks whether a machine can imitate a human in a conversation so that an interrogator cannot tell the difference. The test remains a central concept of artificial intelligence.

Turing argued that the question of whether a machine can think is too vague to answer and should be replaced by the operational test. He anticipated many of the arguments of later debate.

He worked on the design of the Automatic Computing Engine at the National Physical Laboratory. The project was one of the first attempts to build a stored-program computer.

The Persecution and the Legacy

Turing was prosecuted in 1952 for homosexual acts, which were then a criminal offence in Britain. He was convicted and accepted a course of chemical treatment instead of imprisonment.

His security clearance was withdrawn and he was barred from his cryptographic work. He died in 1954 from cyanide poisoning, in circumstances that were ruled a suicide.

He received a formal apology from the British government in 2009 and a royal pardon in 2013. The law that criminalised his conduct was repealed in 1967.

The Turing Award of the Association for Computing Machinery is named in his honour and is regarded as the highest distinction in computer science. His face appears on the fifty-pound note of the Bank of England.

The Morphogenesis and the Reaction-Diffusion

Turing published a paper on the chemical basis of the morphogenesis in 1952. The paper proposed a mechanism for the development of the patterns in the organisms.

The model is based on the interaction of the two chemical substances that diffuse at different rates. The theory is known as the reaction-diffusion system.

The work founded the mathematical biology. The patterns predicted by the theory are observed in the animals and the plants.

The Reputation and the Recognition

Turing is regarded as one of the greatest mathematicians and the most original minds of the twentieth century. His work influenced the computer science, the cryptography, and the artificial intelligence.

The Turing Award is the highest honour in the computer science. The Turing test remains a central concept of the artificial intelligence.

His statue stands at the University of Surrey and at Bletchley Park. The centenary of his birth was celebrated throughout the world in 2012.

See also

• Turing machine
• Turing test
• Bletchley Park
• Artificial intelligence