The Harwell Dekatron, later known as the Wolverhampton Instrument for Teaching Computing from Harwell (WITCH) is the world’s oldest working digital computer. However more than 61 year old world’s oldest working digital computer has been rebooted on November 20, Tuesday, at the UK’s National Museum of Computing (TNMOC) at Bletchley Park. The computer is now working absolutely fine.
The Harwell Dekatron was first constructed in 1949. From 1951, it was used at the Harwell Atomic Energy Research Establishment for processing mathematical calculations for Britain’s nuclear program. But six years later means in 1957, Harwell Dekatron went on retirement. At then this computer was transferred to the Wolverhampton and Staffordshire Technical College and it was renamed Wolverhampton Instrument for Teaching Computation from Harwell (WITCH). It was used at Wolverhampton and Staffordshire Technical College until 1973 and then it was dismantled.
However 39 years later, WITCH (or Harwell Dekatron) has been rebooted at Bletchley Park. It took three years to restore it. Now WITCH is working fine and has already achieved the title “The world’s oldest working digital computer.” Its height is 2 meter and weighs weighs 2.5 tonnes. The system uses 828 flashing Dekatron valves for volatile memory, each capable of holding a single digit; 480 GPO 3000 type relays to shift calculations and six paper tape readers. Since 1951 to 1973, it perfectly calculated addition, subtraction, multiplication and division. But it used to take more time. It took a couple of seconds for addition and subtraction, five seconds for multiplication and up to 15 seconds for division. Here’s a video of WITCH.
Kevin Murrell, a trustee of TNMOC who initiated the restoration project said, “In 1951 the Harwell Dekatron was one of perhaps a dozen computers in the world, and since then it has led a charmed life surviving intact while its contemporaries were recycled or destroyed. As the world’s oldest original working digital computer, it provides a wonderful contrast to our Rebuild of the wartime Colossus, the world’s first semi-programmable electronic computer. The restoration team of the museum has done a superb job to get it working again and it is already proving to be a fascination to young and old alike. To see it in action is to watch the inner workings of a computer — something that is impossible on the machines of today. The restoration has been in full public view and even before it was working again the interest from the public was enormous.”