World’s oldest, working computer to reboot after 48 years

The historic Harwell computer, later known as the WITCH computer, came out of storage last week to travel to The National Museum of Computing at Bletchley Park where it is planned to restore it to full working condition. Once restored by the volunteers at the Museum, it will be the oldest original functioning electronic stored program computer in the world and will be housed alongside the rebuild of Colossus Mk II, the world’s first electronic computer.

The National Museum of Computing TNMOC is inviting members of the public and industry to sponsor the restoration of the Harwell computer by purchasing one of 25 shares at £4500 each. The funds will be used by TNMOC to undertake the restoration and extend the ever-expanding museum. Insight Software has become the first sponsor of the Harwell/WITCH computer restoration project.

The Harwell Computer dates back to 1949 when plans were drawn up for a machine to perform calculations then done by a team of bright young graduates using mechanical calculators. The team’s work had been so tedious that mistakes were inevitable, so the aim was to automate the work. Simplicity, reliability and unattended operation were the design priorities. Speed was a lower priority concern. The machine first ran in 1951. It was a relay-based computer using 900 Dekatron gas-filled tubes that could each hold a single digit in memory -- similar to RAM in a modern computer -- and paper tape for both input and program storage. The Dekatron was described in Elektor March 2008.

The computer was operational at Harwell until 1957, when it was offered in a competition for colleges to see who could make best use of it. Wolverhampton and Staffordshire Technical College (later becoming Wolverhampton University) won and, then becoming known as the WITCH (Wolverhampton Instrument for Teaching Computing from Harwell), it was used in computer education until 1973. After a period on display at Birmingham Science Museum, it was disassembled and put in storage at Birmingham City Council Museums’ Collection Centre. Their curatorial care and attention means it can still be made to work again.

Its arrival at TNMOC on 3 September will be the first stage in an expected year-long restoration challenge. The restoration project is under the aegis of the Computer Conservation Society, who have a long history of successful similar projects.

The current earliest functioning computer is the 1956 Pegasus machine at The Science Museum in London. There are functioning rebuilds of earlier machines, including the Colossus Mk 2 at TNMOC/ Bletchley Park.

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