early computer, built during World War II in England. The exigencies of war gave impetus and funding to computer research. For example, in Britain, the impetus was code breaking. The Ultra project was funded with much secrecy to develop the technology necessary to crack ciphers (cipher) and codes (code) produced by the German electromechanical devices known as the Enigma and the Geheimscheiber (“Secret Writer”). The first code-breaking machine, Colossus, also known as the Mark I, was built at Bletchley Park, a government research centre north of London, and was operational and cracking German codes by December 1943. It employed approximately 1,800 vacuum tubes (electron tube) for computations. Successively larger and more elaborate versions were built over the next two years.

The Ultra project had a gifted mathematician associated with the Bletchley Park effort, and one familiar with codes. Alan Turing (Turing, Alan M.), who had earlier articulated the concept of a universal computing device (known as a Turing machine), may have taken the project further in the direction of a general-purpose device than his government originally had in mind.