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Colossus 10 in Block H at Bletchley Park, the central site for British codebreakers during World War II. Colossus was a set of computers developed by British codebreakers in the years 1943-1945 to help in the cryptanalysis of the Lorenz cipher used by the German Army. Colossus used thermionic valves (vacuum tubes) to perform Boolean and counting operations. Colossus is thus regarded as the world's first programmable, electronic, digital computer, although it was programmed by switches and plugs and not by a stored program. Colossus was designed by research telephone engineer Tommy Flowers. Alan Turing's use of probability in cryptanalysis contributed to its design. It has sometimes been erroneously stated that Turing designed Colossus to aid the cryptanalysis of the Enigma. Turing's machine that helped decode Enigma was the electromechanical Bombe, not Colossus.
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