Page last updated at 08:13 GMT, Thursday, 3 September 2009 09:13 UK

Reboot for UK's 'oldest' computer


Kevin Murrell describes how the computer is being rebuilt

Britain's oldest original computer, the Harwell, is being sent to the National Museum of Computing at Bletchley where it is to be restored to working order.

The computer, which was designed in 1949, first ran in 1951 and was designed to perform mathematical calculations; it lasted until 1973.

When first built the 2.4m x 5m computer was state-of-the-art, although it was superseded by transistor-based systems.

The restoration project is expected to take a year.

The system was built and used by staff at the Atomic Energy Research Establishment in Harwell, Oxfordshire.

Speaking to BBC News, Dick Barnes, who helped build the original Harwell computer, said the research was - officially at least - for civilian nuclear power projects.

"Officially it was to help with general background atomic theory and to assist in the development of civilian power," he said.

"Of course, it [the Atomic Energy Research Establishment] had connections to the nuclear weapons programme," he added.

Although not the first computer built in the UK, the Harwell had one of the longest service lives.

Built by a team of three people, the device was capable of doing the work of six to ten people and ran for seven years until the establishment obtained their first commercial computer.

"We didn't think we were doing anything pioneering at the time," said Mr Barnes.

"We knew the Manchester Baby and Cambridge's EDSAC were already up and running. Both these projects had large teams and we felt like a poor relation.

"Looking back, hardly any of us were computer literate and it's astonishing that we managed stored computing at all," he said.

The Harwell machine is recognisably modern in that unlike some of its predecessors such as Colossus it used a single memory to store data and programs.

Harwell computer
The Harwell computer was still in use in 1973

Kevin Murrell, director of The National Museum of Computing at Bletchley Park, said it had some of the characteristics of contemporary machines.

"The machine 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."

Time line

Retired from service at Harwell, the system was offered as a prize for colleges, with Wolverhampton and Staffordshire Technical College (later Wolverhampton University) taking ownership and renaming it as the WITCH (Wolverhampton Instrument for Teaching Computing from Harwell). It was used in computer education until 1973.

It then went on display at Birmingham Science Museum, before being put in storage at Birmingham City Council Museums' Collection Centre.

Now it is being sent to the National Museum of Computing in Bletchley, where a team are set to restore it to working order.

Mr Barnes said the prospect of seeing the Harwell computer up and running after more than 36 years was "very exciting".

"I still don't know how they managed to find so many spare parts, but I think they have a very good chance of getting it going again," he said.

There are several significant predecessors to the Harwell computer: The Ace (parts of which are on display in London's Science Museum), the Electronic Delay Storage Automatic Calculator (EDSAC) which was broken up, and Manchester's Small-Scale Experimental Machine (SSEM) nicknamed Baby, which has been rebuilt but not using original parts.

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