Colossus Colossus was designed and built at the Post Office Research Laboratories at Dollis Hill in North London in 1943 by a team led by Dr Tommy Flowers to help Bletchley Park in decoding the intercepted German telegraphic cipher traffic enciphered using the Lorenz SZ42 cipher machine. This cipher machine enciphered electrical teleprinter signals which used the international 5-bit Baudot teleprinter code. It enciphered the input plain text by adding to it successively two characters before …showed first 75 words of 323 total…

…showed last 75 words of 323 total…and after D Day in 1944. Colossus was the world's first large electronic valve programmable logic calculator. Not just one but ten of them were built and operational in Bletchley Park. Colossus found the wheel settings used by the German Lorenz machine operator for a particular message. When these had been found, which took about two hours, they were plugged up on the Tunny machine. It was this machine which actually deciphered the message. ------------------------------------------------------------------------ **Bibliography**