Colossus celebrates 70th anniversary at National Museum of Computing

World's first electronic computing ran for the first time 70 years ago today.
Written by Colin Barker, Contributor

Tommy Flowers would no doubt be pleased if he knew that his most famous achievement, the building of the world's first electronic computer, Colossus, is still being celebrated 70 years to the day it ran its first program.

Today, Colossus veterans and their families gathered at The National Museum of Computing in Bletchley Park to celebrate the anniversary and to mark the achievement they will see a re-enactment of the code-breaking process, from intercept to decrypt, done with a working rebuild of Colossus.

On 5 February 1944, Colossus Mk I attacked its first Lorenz-encrypted message, the highly sophisticated cipher used in communications between Hitler and his generals in World War II. Bletchley Park had already cracked the Enigma code but at that time the Lorenz code was proving tougher to crack, being based on 32-symbol Baudot code as opposed to Enigma's 26-letter code.

The machine and the code were designed by British telephone engineer Tommy Flowers, who was the son of a bricklayer and worked at the Royal Arsenal, Woolwich. He learned mechanical engineering before taking night classes in electronic engineering.

Flowers designed Colossus with the intention of speeding up the code-breaking effort, and by the end of the war there were 10 functioning Colossi helping with the war effort. However, little was known about these machines and news of their existence was kept secret. At the end of the war eight of the 10 machines were scrapped and their existence remained secret for the next 30 years.

Colossus was well named as it occupied the size of a living room (7ft high by 17ft wide and 11ft deep) and weighed five tonnes. It used 8kW of power and it incorporated 2,500 valves — 501 of which were thyraton (controlled gas rectifier) switches — about 100 logic gates and 10,000 resistors connected by 7km of wiring.

Colossus could handle an estimated 5,000 characters per second, an outstanding achievement in its day.

Tim Reynolds, Chair of The National Museum of Computing, paid tribute to all who played their part in building Colossus — including Bill Tutte, who deducted how the Lorenz machine worked without ever having seen one, as well as many cryptologists who broke the cipher by hand.,

"The working Colossus rebuilt by the late Tony Sale and his team provides a mesmerising start to our story of the history of computing at The National Museum of Computing," Reynolds said. " It fascinates people of all ages and we see on a daily basis the inspiration that it provides to school groups who visit the museum."

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