The machine cranked through the boring calculations atomic scientists once had to do
Kevin Murrell who discovered the computer explains how it was brought back to life
The world's oldest
original working digital computer is going on display at The National
Museum of Computing in Buckinghamshire.
The Witch, as the machine is known, has been restored to clattering and flashing life in a three-year effort.
In its heyday in the 1950s the machine was the workhorse of the UK's atomic energy research programme.
A happy accident led to its discovery in a municipal storeroom where it had languished for 15 years.
Cleaning up
The machine will make its official public debut at a special
ceremony at The National Museum of Computing (TNMOC) in Bletchley Park
on 20 November. Attending the unveiling will be some of its creators as
well as staff that used it and students who cut their programming teeth
on the machine.
Design and construction work on the machine began in 1949 and
it was built to aid scientists working at the UK's Atomic Energy
Research Establishment at Harwell in Oxfordshire. The 2.5 tonne machine
was created to ease the burden on scientists by doing electronically the
calculations that previously were done using adding machines.
The machine first ran in 1951 and was known as the Harwell Dekatron -
so named for the valves it used as a memory store. Although slow - the
machine took up to 10 seconds to multiply two numbers - it proved very
reliable and often cranked up 80 hours of running time in a week.
By 1957 the machine was being outstripped by faster, smaller
computers and it was handed over to the Wolverhampton and Staffordshire
Technical College (more recently Wolverhampton University) where it was
used to teach programming and began to be called the Witch
(Wolverhampton Instrument for Teaching Computation from Harwell).
In 1973 it was donated to Birmingham's Museum of Science and
Industry and was on show for 24 years until 1997 when the museum closed
and the machine was dismantled and put into storage.
By chance Kevin Murrell, one of the TNMOC's trustees, spotted the
control panel of the Witch in a photograph taken by another computer
conservationist who had been in the municipal store seeking components
for a different machine.
Mr Murrell said that as a "geeky teenager" he had regularly
seen the Witch during many trips to the museum and instantly recognised
its parts in the background of the photograph.
On subsequent trips to the storage facility the various parts
of the Witch were found, retrieved and then taken to the museum at
Bletchley where restoration began.
The restoration effort was led by conservationist Delwyn
Holroyd who said it was "pretty dirty" when the machine first arrived at
Bletchley. Remarkably, he said, it had not suffered too much physical
damage and the restoration team has been at pains to replace as little
as possible. The vast majority of the parts on the machine, including
its 480 relays and 828 Dekatron tubes, are entirely original, he said.
Said Mr Murrell: "It's important for us to have a machine
like this back in working order as it gives us an understanding of the
state of technology in the late 1940s in Britain."