Saturday, 24 November 2012 15:30

WITCH rebooted after 39 years

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WITCH computer 640

The oldest active digital computer in the world, the British WITCH (Wolverhampton Instrument for Teaching Computing from Harwell), after 39 years idle, has been put into operation once more at the National Museum of Computing at Bletchley Park. For those who do not know, Bletchley Park was home to Britain's top math and computer brains during the Second World War, including Alan Turing, and a place where the code for the German Enigma was broken. It is also where the first use electromechanical computers happened. Bletchley Park has been converted into a national museum of computing and the latest exhibit is the oldest digital computer ever to function.

WITCH began to operate under the codename Harwell back in 1951 and until 1957 was used mainly for calculations in atomic research. The data was received from punch tape and output was on teleprinters or still more punched tape. After the first atomic tests in 1957; It was committed to the University of Wolverhampton, where it was given a new name “WITCH” and there was used until 1973. After that it was stored in the Birmingham Museum until 1997 as a static exhibit (it was not in operation) and then stored in a warehouse where it was completely forgotten about until 2009.
witch 50s
Now, three years later, the WITCH is recovered and returned to operation. An interesting fact about it is that it does not work with binary base as most digital computers, but with a decimal. This is provided by dekatrons, vacuum tubes that save (in the form of different voltage levels), the numbers 0 through 9, and are divided into 40 batteries with 8 tubes each. This means that it is able to present 40 eight-digit decimal numbers. This system has not proven to be particularly effective and thus to multiply two numbers it takes WITCH 5 to 10 seconds. Its advantage is, of course, that it can work continuously for hours and days. Apparently in the 50's it worked non-stop throughout the Christmas and New Year holidays, with no oversight, having read the miles of punched tape and giving very accurate results.

It is interesting that although WITCH is the oldest, there are still a lot active “ancient” computers. Referred to as DEC PDP computers that are still used in the British and U.S. military, computers aboard the space probes Pioneer and Voyager spacecraft, and LGM-30 Minuteman - a computer in U.S. intercontinental nuclear missiles made in the 70's who are still caring for these missiles. It looks like the old school still has something to say.

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Read 3187 times Last modified on Saturday, 24 November 2012 15:42

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