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 (the first electromechanical being Konrad Zuse's Z3 completed in Berlin in 1941), although it was programmed by switches and plugs and not by a stored program.
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.