Information Technology Reference
In-Depth Information
A large team of engineers and mathematicians worked for two years on build-
ing the Colossus. When finished in 1943, it was the first operational computer in
Great Britain and a contender for being the first operational computer in the world.
Note
In 2006, a working replica of the Colossus was created and was
entered in a code-breaking contest against modern notebook com-
puters. Although Colossus did not win, it had very respectable res-
ults for a device designed using 1940s technology.
The British code-breaking program was called the Ultra program. The deriva-
tion of the word “ultra” implied that the secrecy was even higher than top secret,
so it was “ultra secret.” Some of the information about the Ultra program was not
declassified until 1972, which means that early work on digital computers as part
of Ultra was not widely known. Senior officers from both the United States and
the United Kingdom credit the Ultra program with shortening the war by perhaps
two years. A few even state that the war might have been lost if not for Ultra.
In 1946, Alan Turing presented a paper, written in 1945, to the executive com-
mittee of the British National Physical Laboratory. The title was “Automatic Com-
puting Engine” (ACE). It described a very sophisticated stored-program digital
computer. Because Turing's work was covered by the Official Secrets Act, he was
prevented from publishing the paper or making the contents known.
The proposed Turing computer features subroutine calls, which were not in
the Electronic Discrete Variable Automatic Computer (EDVAC), described by von
Neumann in his 1945 paper. This means that the Turing computer was somewhat
in advance of the EDVAC. Turing also defined a programming language in a sec-
tion of his report titled “Abbreviated Computer Instructions.”
Because of secrecy, a working computer based on Turing's ACE concepts was
not built until 1950, when it was the fastest computer constructed up until that
time. This was named the Pilot Model ACE and it became operational on May 10,
1950. This computer used vacuum tubes for computation and mercury delay lines
for memory.
A larger version called MOSAIC, which stood for Ministry of Supply Auto-
matic Integrator and Computer, was completed in 1952, and some of the details of
this device remain classified even today. It was used to support radar sightings of
aircraft and to compute their future flight paths.
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