THE WORLD'S OLDEST working digital computer, the Harwell
Dekatron or 'Witch' will be rebooted today at the National
Museum of Computing at Bletchley Park. The Witch is being
rebooted at Bletchley Park after a three year restoration
project. It was originally built in 1951, is 2 metres high and
weighs 2.5 tonnes. Unlike today's computers the Witch is
something of an event machine, and its fitting that you can go
and see it in a museum. It has 828 flashing Dekatron valves, 480
relays and a bank of paper tape readers. "In 1951 the Harwell
Dekatron was one of perhaps a dozen computers in the world, and
since then it has led a charmed life surviving intact while its
contemporaries were recycled or destroyed," said Kevin Murrell,
trustee of the museum. "As the world's oldest original working
digital computer, it provides a wonderful contrast to our
Rebuild of the wartime Colossus, the world's first semi-
programmable electronic computer." When it was built the Witch
worked at the Harwell Atomic Energy Research Estab