The Harwell Dekatron computer is a 1950s computer having roughly the weight and size of a Hummer H3 and the computing power of a four-function pocket calculator. Having been restored to its original operating condition using 95 percent original parts, it is now the oldest functioning programmable digital computer in the world. Guinness might have been onto something, when, in 1973, they named the Dekatron the Most Durable Computer in the World.
The Harwell computer was built in the early 1950s for the UK Atomic Energy Research Establishment. Never intended to be a state-of-the-art general-purpose computer, the Harwell was developed to perform simple but repetitive calculations continuously and without error. Its computational rate is about 0.1 FLOPS, similar to that of a pocket calculator, but the computer operates for long periods of time without human intervention.
The computational needs of the Establishment soon outstripped the Harwell, and in 1957 Wolverhampton University was offered the machine to train students about computing. The Harwell was relaunched as the WITCH (Wolverhampton Instrument for Teaching Computing from Harwell), and helped a generation of students learn about computing. But by 1974, Wolverhampton decided that the WITCH was obsolete. They donated the computer to the Museum of Science and Industry in Birmingham, where it was on display until the museum closed in 1997.
Then, once again evading disposal, the computer was disassembled and stored in the Birmingham City Council Museums Collection Centre. Rediscovered quite by accident in 2008 by Kevin Murrell, a trustee of the National Museum of Computing, it was moved to its current home at that museum, where it’s been restored to full functionality…
A dekatron was the simplest base-10 counter able to add and subtract while generating carry digits. Common dekatrons were based on decimal counting, and could switch reliably at speeds in excess of 10 kHz. Dekatrons are triggered to consecutively light a set of ten positions in a cold-cathode tube.
Surely a delightful example of change and efficiency in technology. There are beaucoup constructions that haven’t changed greatly in size because what they store or manipulate hasn’t changed, e.g., automobiles and homes. But, manipulating data to draw conclusions has probably changed more dramatically than any other construct over time.