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Birth of the digital computer
Colossus was an electronic digital computer, built during WWII from over 1700
valves (tubes). It was used to break the codes of the
German Lorenz SZ-40 cipher machine
that was used by the German High Command.
Colossus is sometimes referred to as the world's first programmable, digital,
electronic, computer. In any case, it was conceived before the American
ENIAC.
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Colossus was designed by Tommy Flowers of the
Post Office Research Station (part of the General Post Office,
GPO) at Dollis Hill (UK), with input from Harry Fensom, Allen Coombs,
Sid Broadhurst and Bill Chandler.
It was used to solve a problem posed by Max Newman,
one of the codebreakers at Bletchley Park.
The image on the right shows one of only eight photographs of an original
Colossus Mark II, taken during WWII. The photographs were used by Tony Sale
and his team to start the Colossus Rebuild Project in 1993.
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One of the most prominent parts of Colossus is the input device on the right,
nicknamed 'the bedstead'. It is an optical reader for punched paper tapes, than
can read data at the phenomenal speed of 5000 characters per second!
A complex system of supporting wheels is necessary to prevent the tape from
ripping apart at this speed.
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Immediately after WWII, most Colossus computers were ordered to be demolished.
They were either destroyed or dismantled. A few machines were held back for
future use, but eventually these were destroyed as well, as and when newer
technologies emerged.
In 1991, a team led by Tony Sale started playing with the thought that it
might be possible to rebuild a fully operational Colossus computer.
Eventually, in 1993, he set out to start the rebuild project, based on the
very limited amount of information that he gathered.
The first parts of Colossus were switched-on on 6 June 1996, in the presence
of HRH the Duke of Kent and the original designer Tommy Flowers.
In November 2007, the Colossus-I rebuild project was completed and the
machine was staged in a Cipher Challenge contest.
Since then, work has started to convert Colossus-I into Colossus-II.
As the Mark II version contains over 1000 more valves than the
original machine, this project will, no doubt,
keep Tony and his team busy for the next couple of years.
Below are some photographs of Colossus that we took in November 2004.
We apologize for the rather poor quality; at the time we were still using
an analog camera.
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It is sometimes assumed, even by respected writers, that Colossus was used
to break the German Enigma codes. However, this was
not the case. Colossus was used to break the codes of a far more advanced
machine: the Lorenz SZ-42, used by Hitler's High Command.
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Enigma was instead broken with help of the electro-mechanical Bombe,
designed by Alan Turing and Gordon Welchman at Bletchley Park.
Over 200 of these machines were installed at Bletchley Park and its
outposts, to attack the German Enigma messages on a daily bases.
 More information
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© Copyright 2009-2012, Paul Reuvers & Marc Simons. Last changed: Mon,14 May 2012.09:37:31
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