Alan Turing was a physicist and mathematician most notably known to have cracked the code of the German ENIGMA machine. A means of commanders contacting the dreaded U-Boats that was encoded to the point that seizing and decoding the machine was the only way British shipping could be safe on the open seas. Turing also did work on primitive computers
Together with another mathematician W G Welchman, Turing developed the Bombe, a machine based on earlier work by Polish mathematicians, which from late 1940 was decoding all messages sent by the Enigma machines of the Luftwaffe. The Enigma machines of the German navy were much harder to break but this was the type of challenge which Turing enjoyed. By the middle of 1941 Turing's statistical approach, together with captured information, had led to the German navy signals being decoded at Bletchley.Obviously this was a brilliant man working on many variations of mathematics to create computers that are primitive by our standards but basically on/off circuits now larger than most towers. They were laid out in rows and switched over by hand initially.
From November 1942 until March 1943 Turing was in the United States liaising over decoding issues and also on a speech secrecy system. Changes in the way the Germans encoded their messages had meant that Bletchley lost the ability to decode the messages. Turing was not directly involved with the successful breaking of these more complex codes, but his ideas proved of the greatest importance in this work. Turing was awarded the O.B.E. in 1945 for his vital contribution to the war effort.
At the end of the war Turing was invited by the National Physical Laboratory in London to design a computer. His report proposing the Automatic Computing Engine (ACE) was submitted in March 1946. Turing's design was at that point an original detailed design and prospectus for a computer in the modern sense. The size of storage he planned for the ACE was regarded by most who considered the report as hopelessly over-ambitious and there were delays in the project being approved.
He was caught with a male lover and charged as if he was a criminal. He tried taking estrogens under court order to avoid prison. He was found dead with an arsenic laced apple shortly after.