Colossus computer

Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves (vacuum tubes) to perform Boolean and counting operations. Colossus is regarded as the world's first programmable, electronic, digital computer. There were earlier electromechanical computers, the first being Konrad Zuse's Z3, completed in Berlin in 1941. Colossus was designed by General Post Office (GPO) research telephone engineer Tommy Flowers, based on plans developed by mathematician Max Newman at the Government Code and Cypher School at Bletchley Park. Alan Turing's use of probability in cryptanalysis (see Banburismus) contributed to its design. It is sometimes erroneously said that Colossus was designed by Turing, not Flowers, to aid the cryptanalysis of the Enigma but an earlier machine that Turing designed was the electromechanical Bombe. The prototype, Colossus Mark 1, was working by December 1943 and was in use at Bletchley Park by early 1944. An improved Colossus Mark 2 which used shift registers to run five times faster first ran successfully on 1 June 1944, just in time for the Normandy landings on D-Day. Ten Colossus machines were in use by the end of the war and an eleventh was being commissioned. Bletchley Park's use of these machines allowed the Allies to obtain a vast amount of high-level military intelligence from intercepted radiotelegraphy messages between the German High Command (OKW) and their army commands throughout occupied Europe. The existence of the Colossus machines was kept secret until the mid-1970s. All but two machines were dismantled into such small parts that their use could not be inferred. The two retained machines were eventually dismantled in the 1960s. In January 2024, new photos were released by GCHQ that showed re-engineered Colossus in a very different environment from the Bletchley Park buildings, presumably at GCHQ Cheltenham. A functioning reconstruction of a Mark 2 Colossus was completed in 2008 by Tony Sale and a team of volunteers; it is on display in The National Museum of Computing at Bletchley Park, where it is regularly demonstrated to visitors.

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