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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 fixed program, digital,
electronic, computer. In any case, it was conceived before the American
ENIAC.
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Colossus was designed by Tommy Flowers,
an electronics engineer 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,
a codebreaker at Bletchley Park.
The image on the right shows one of just eight photographs
of an original Colossus Mark II in action that were taken during WWII.
The images were used in 1993 by Tony Sale
and his team of volunteers, to start the
Colossus Rebuild Project.
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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 regulate the
tape tension and prevent the tape from ripping apart at this speed.
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Contrary to popular believe, Colossus was not used to break the
German Enigma machine.
The Enigma was broken by means of an
electro-mechanical machine, known as the
Bombe, designed
by Alan Turing and Gordon Welchman.
Colossus on the other hand,
was used to break the Lorenz SZ-40/42.
A highly sophisticated teleprinter attachment with no less than
twelve complex cipher wheels. It was used by the German High
Command for messages at the highest level, for example between Hitler and
Field Marshal Rommel in North Africa.
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Immediately after WWII, most Colossus computers were ordered to be demolished.
They were either destroyed or dismantled and the components were reused.
Two machines were kept for future use by GCHQ during the Cold War.
In 1959 and 1960, when newer technologies had emerged, these two
machines were finally decomissioned and were eventually dismantled.
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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.
In 1993, he set out to start the rebuild project, based on the
very limited information that he had 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.
The latter passed away in 1998 at the age of 92.
In November 2007, the rebuild project was completed and Colossus
was staged in an international Cipher Challenge contest.
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Since then, work has started to convert Colossus (now called Colossus-I)
into Colossus Mark II.
As the Mark II version contains over 1000 more valves than the
original machine, this project would, no doubt,
keep Tony and his team busy for the next couple of years.
Sadly, Tony Sale passed away
unexpectedly on 28 August 2011 at the age of 80, leaving behind
the Colossus legacy.
Luckily though, his achievement was well-documented so that his
team could complete the work.
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Tony's legacy has been preserved well.
In 2012, the Colossus display in H-Block at Bletchley Park has been
refurbished completely. The ceiling has been painted black and the
floor has received a new carpet. More importantly, there is now much
more room for the audience, who can walk all around Colossus now.
The image above shows Colossus in September 2013 during a presentation
by volunteer Kevin Coleman. At the very left is Chief Colossus Engineer
Phil Hayes.
As it is now possible to walk around Colossus, you can 'view through'
the machine and see the many, many wires, stepping relais, and thermionic
valves (vacuum tubes) behind the front panel.
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If you are interested in electronics, computer technology, history
of WWII, etc., Colossus is a must see. Only when you are
physically inside the room where Colossus is located, can you appreciate
the efforts of its designers, but also of its re-builders. You can see
it in action, feel the heat generated by the valves and sense the
typical smell of working electronics. If you are visiting Bletchley Park,
you must take some time to visit The National Museum of Computing
(TNMOC) in Block H. The volunteers will be
more than willing to tell you all you want to know about Colossus.
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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. This was
not the case however. Colossus was used to break the codes of the far more
advanced Lorenz SZ-42, used by Hitler's High
Command (Oberst Kommando des Heeres).
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Enigma instead, was broken with help of an electro-mechanical machine,
called the Bombe,
designed by Alan Turing and Gordon Welchman at Bletchley Park
and built by Harold (Doc) Keen at the British Tabulating Company (BTC).
Over 200 of these machines were installed at Bletchley Park and its
outposts, attacking the German Enigma messages on a daily basis.
 More information
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Saturday, 11 January 2014 - 12:51 CET
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![Tony Sale in front of Colossus. Copyright South Beds News [4].](img/tony_sale_full.jpg "Tony Sale in front of Colossus. Copyright South Beds News [4].")
