Photos: Restoring one of the world's oldest computers

Work began this week on restoring what will be the world's oldest working stored-program electronic computer.

Volunteers at The National Museum of Computing (TNMOC) at Bletchley Park will rebuild the Witch machine (shown here) - a computer that was first used in 1951 for atomic research.

Witch - the Wolverhampton Instrument for Teaching Computing from Harwell - was based on telephone exchange relays and 900 Dekatron gas-filled tubes, which could each hold a single digit in memory. Paper tape was used to both input data for and store the output of the machine.

The device is not the oldest electronic calculating device but is regarded as the first modern computer still capable of working.

The machine was built and used by the Atomic Energy Research Establishment in Harwell, Oxfordshire and went on to be used as a teaching aid at a college in Wolverhampton until 1973.

See more photos from Bletchley Park here.

Photo credit: Nuclear Decommissioning Authority