Restoration starts on one of 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 at Bletchley Park--about 50 miles northwest of London--will rebuild the Witch machine--a computer first used in 1951 for atomic research.

Witch, or 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.

The machine was developed to automate laborious mathematical calculations at the Harwell facility. Witch, also known as the Harwell computer, could solve algorithms at roughly the same speed as a single human mathematician using a mechanical calculator.

The restoration work is expected to take a year, when Witch will then go on display at the National Museum of Computing, which already holds the world's first electronic computer, the Colossus Mark II.

Kevin Murrell, director and trustee of the museum, said its engineers are keen to start restoring the Witch machine.

"For most of them this will be the toughest project yet. It's the computing equivalent of the raising of the Mary Rose and they are up to challenge," he said in a statement.

The museum is asking members of the public and industry to sponsor the restoration of the Harwell computer by purchasing one of 25 shares at 4,500 pounds (about $7,300) each. Insight Software has become the first sponsor of the restoration project.

Nick Heath of Silicon.com reports from London.