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World’s oldest working digital computer gets rebooted

The oldest digital computer in the world, the Harwell Dekatron, has been brought back to life after fifteen years of dormancy. The giant computer was switched back on at a ceremony held at the National Museum of Computing (TNMOC) in Buckinghamshire, with two of the computer's original developers in attendance.

The historical piece of hardware, also known as the WITCH - the Wolverhampton Instrument for Teaching Computation from Harwell – weighs in at 2.5 tonnes. It operates on 828 Dekatron valves that display its decimal output, six paper tape readers and 480 GPO 3000 type relays.

Built in 1949 for the purpose of formulating mathematical calculations, it was originally based at the UK's Harwell Atomic Energy Research Establishment, where it began its operation cycle in 1951.

The machine could work out equations involving division at a rate of 15 seconds, multiplication at five seconds, while subtraction and addition took 'a couple' of seconds, according to the museum.

It was finally placed in storage in 1997 but was rediscovered four years ago by TNMOC trustee Kevin Murrell.

"I caught a glimpse of its control panel in a photograph of stored equipment. That sparked our ideas to rescue it and we hunted it down," said Murrell.

The restoration process took three years, as many of the components needed to get the Harwell back in working order were no longer available.

"The restoration was quite a challenge requiring work with components like valves, relays and paper tape readers that are rarely seen these days and are certainly not found in modern computers. Older members of the team had to brush up on old skills while younger members had to learn from scratch," said TNMOC lead volunteer, Delwyn Holroyd.