The world’s oldest still working digital computer, the Wolverhampton Instrument for Teaching Computing from Harwell (WITCH), also known as the Harwell Dekatron Computer or simply as the Harwell Computer, was put into operation again after a three-year restoration at The National Museum of Computing (TNMOC) in England.
The construction of the Harwell computer started in 1949 with the purpose of being used by the scientists at the Atomic Energy Research Establishment at Harwell, Oxfordshire. Activated in 1951, it weighs about 2.5 tons, it uses 828 Dekatron tubes for memory, 480 relays and punched tape for programming. The output is printed by a teleprinter.
Its performances are not exactly those of a modern computer and not even of any cheap pocket calculator. In fact, to perform a simple multiplication it takes from 5 to 10 seconds. The advantage is that the Harwell computer can be programmed and work for a long time making a series of preprogrammed calculations that can be very long. In the years of its greatest use, in fact, it was used for an average of 80 hours a week.
Even then the progress in information technology were rapid and in 1957 the Harwell computer had become obsolete. Therefore they launched a competition among colleges to decide who to give it to, as it could still be useful for other purposes. The Wolverhampton and Staffordshire Technical College, which later became Wolverhampton University, won and used it for the teaching of computer science. It was then that the computer was named WITCH.
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In 1973, the WITCH computer was donated to the Museum of Science and Industry in Birmingham, where it remained until 1997, when the museum closed. At that point, it was dismantled and its components stored in the Birmingham City Council Museums Collection Centre, in what appeared to be the end of its life.
Kevin Murrell, a trustee of The National Museum of Computing, by chance saw a picture of the control panel of the WITCH computer and managed to have it restored. Luckily, the physical damage was limited nonetheless the work was very long.
The WITCH computer is truly a piece of computer science history and can now be admired by the public during the hours of opening of The National Museum of Computing. That’s a great opportunity to get an idea of how much progress has been made in the 60 years passed since it’s been put into operation for the first time.
