The Harwell Dekatron Computer - the book

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New TNMOC book tells the story of the world's oldest working digital computer

The National Museum of Computing has published a book tracing the fascinating and varied history of the Harwell Dekatron / WITCH, the world's oldest working digital computer, which was restored and rebooted at the Museum in 2012.

The Harwell Dekatron Computer, by Kevin Murrell who rediscovered the Dekatron computer, and Delwyn Holroyd, who led the restoration team that brought the machine back to life, tells the story of the machine that has led a charmed life and defied the recyclers across seven decades to find a practical use again in 2013. It draws on the memories of many of those involved with the machine across the years from the original designers through users across the years to today's conservation team.

Buy the book here

Designed in 1949 and first operational in 1951, the Harwell Dekatron was one of perhaps a dozen computers in the world at that time. As big as the wall of a living room, it clattered and flashed as it performed the work of human "computors" using hand calculators at Harwell from 1951-57.

Instead of being consigned to the recyclers when it became obsolete, it was offered in a competition to the educational establishment proposing the best use for it. Wolverhampton Institute of Technology recognised its potential in education, won the machine and renamed it the WITCH (the Wolverhampton Instrument for Teaching Computation from Harwell). It operated there until 1973 when it was retired for a second time to a Birmingham museum and subsequently dismantled and left largely forgotten in safe storage.

Rediscovered by chance by TNMOC trustee Kevin Murrell in 2008, it was brought to TNMOC where it was restored and brought back to life much to the amazement of the world's media in November 2012.

Today, apart from being a star attraction at TNMOC, it is again used in education to show the beginnings of our information age and to enable students to see the dramatic inner workings of the world's oldest working digital computer.

The Harwell Dekatron Computer book, with 40 pages and more than 50 period and modern images, is available onsite at The National Museum of Computing shop for £6 and through

Buy the book here

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