Colossus was the world's first programmable, electronic, digital computer. The Colossus computers were developed for British codebreakers during World War II to help in the cryptanalysis of the Lorenz cipher.
Mk 1: December 1, 1943
Operational at Bletchley Park by February 5, 1944
Mk 2: June 1, 1944
Discontinued: June 8, 1945