Harwell Dekatron WITCH 2

World’s Oldest Digital Computer Restored At National Museum Of Computing

The Harwell Dekatron (WITCH) goes on display after three year restoration project

On by Steve McCaskill 0

The world’s oldest original digital computer has gone on display at The National Museum of Computing (TMNOC), following a three-year restoration project.

TMNOC is an independent charity housing the largest collection of functional historic computers in Europe and the 61-year old Harwell Dekatron (WITCH) can now be viewed by the general public whenever the museum is open.

The 2.5 tonne, computer has 828 Dekatron valves, 480 relays and banks of paper tape readers and will be brought back into operation in the presence of two of the original designers.

Harwell Dekatron on show

“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 TNMOC who initiated the restoration project. “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.”

“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,” said Delwyn Holroyd, a volunteer at The National Museum of Computing who led the restoration team. “Older members of the team had to brush up on old skills while younger members had to learn from scratch!”

The designing of the computer began in 1949 and it was first run in 1951 at Harwell Atomic Energy Research Establishment where it automated calculations that were previously performed with hand calculators.

The National Museum of Computing restoration

After it became redundant at Harwell, a competition was held for educational establishments to receive the computer. Wolverhampton and Staffordshire Technical College won, renamed it WITCH (Wolverhampton Instrument for Teaching Computation from Harwell), and used it until 1973.WITCH

It was then displayed at the Birmingham Museum of Science and Industry before being put into storage. A team of volunteers from TMNOC rediscovered it in 2008 and formulated a restoration plan.

“When that Museum closed, it disappeared from public view, but four years ago quite by chance I caught a glimpse of its control panel in a photograph of stored equipment,” said Murrell. “That sparked our ideas to rescue it and we hunted it down.”

“The TNMOC restoration team has done a superb job to get it working again and it is already proving to be a fascination to young and old alike,” he added. “The restoration has been in full public view and even before it was working again the interest from the public was enormous.”

What do you know about British computing history? Try our Alan Turing quiz!

Steve McCaskill
Author: Steve McCaskill
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