Alan Turing, born 23 June 1912, is famous for his key role in breaking German codes in World War II. But for mathematicians, his greatest work was on the invention of the computer.

Alan Turing's brilliance at maths was spectacular. Aged 22, just a year after his graduation, he was elected a fellow of King's College Cambridge. And it was just a year after that, that he turned his attention to problems in the foundations of mathematics and ended up showing that a simple machine, set up to read and write numbers and to run a few basic functions, could in principle do all the things that are do-able in mathematics. His 'universal' machine was just a concept - a paper tape that could be read, interpreted and acted on robotically. But the concept was profound.

World War II shortly afterwards took Turing's talents into other directions, but even while designing machines at Bletchley Park to break the German Enigma codes, he was wondering how much more a computing machine might do - play c

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