December 8: The first trial run of Colossus at Bletchley Park (1943)

Colossus Mark II

Colossus Mark 1, the world's first electronic digital programmable computer, had its first trial run at Bletchley Park, which was the UK's code breaking centre during the World War II. Colossus was designed by Thomas H. Flowers at the Post Office Research Station, Dollis Hill and then moved to Bletchley Park. Colossus computers were mainly used to find the key combinations of German rotor cipher devices such as Lorenz cipher machines and Enigma machines. The central processing unit consisted of about 1,500 thermionic values and thyratrons. The input media was paper tape and output devices were teleprinters and indicator lamp display panels. There was no memory device in it. The operation of Colossus computers were ceased on June 8, 1945. It was pity to discontinue the operation of Colossus computers, however, the people worked on the projects at Bletchley Park have significantly contributed to the progress of computer science and engineering.  Jack Copeland's book about Colossus is an interesting read.