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 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.
A Colossus Mark 2 computer being operated by Wrens. The slanted control panel on the left was used to set the "pin" (or "cam") patterns of the Lorenz. The "bedstead" paper tape transport is on the right. | |
| Developer | Tommy Flowers, assisted by Sidney Broadhurst, William Chandler and for the Mark 2 machines, Allen Coombs |
|---|---|
| Manufacturer | Post Office Research Station |
| Type | Special-purpose electronic digital programmable computer |
| Generation | First-generation computer |
| Release date |
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| Discontinued | 1960 |
| Units shipped | 12 |
| Media |
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| CPU | Custom circuits using thermionic valves and thyratrons. A total of 1,600 in Mk 1 and 2,400 in Mk 2. Also relays and stepping switches |
| Memory | None (no RAM) |
| Display | Indicator lamp panel |
| Input | Paper tape of up to 20,000 × 5-bit characters in a continuous loop |
| Power | 8.5 kW |
Colossus was designed by General Post Office (GPO) research telephone engineer Tommy Flowers to solve a problem posed by mathematician Max Newman at the Government Code and Cypher School (GC&CS) at Bletchley Park.
Alan Turing's use of probability in cryptanalysis (see Banburismus) 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.)
The prototype, Colossus Mark 1, was shown to be working in December 1943 and was in use at Bletchley Park by early 1944. An improved Colossus Mark 2 that used shift registers to quintuple the processing speed, first worked on 1 June 1944, just in time for the Normandy landings on D-Day. Ten Colossi 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 at The National Museum of Computing on Bletchley Park.