Computer ◆ Conservation ◆ Society

WITCH, the third computer built in this country, has retired

Cecil Ramsbottom
Electrical Engineering Department

Wolverhampton and Staffordshire College of Technology

From Polytechnic Staff Newsletter Vol. 6 - 1973


Designed by R.C.M. Barnes & E. Cooke Yarborough for calculations concerned with nuclear research and known as the Harwell Dekatron Computer, she had twenty stores when construction began in 1947. When displaced by one of the early commercially built computers, WITCH was offered as a gift, through the Oxford Mathematical Institute, to the college which could present the best case for its future use. At that time, Roy Wooldridge, now Principal at Derby, was a Senior Lecturer in Mathematics. He collected information about possible uses by schools, local industry, and college; I presented a paper about spares and maintenance. Ted Mitchell was among those who represented us at the interview.

WITCH came to us when there were only seventeen computers in the country; the packing cases occupied Room 31 and even then she attracted visitors. Assembly in Room 30A took just a week. Roy Wooldridge prepared a short programme - simply to square 1.3. On Tuesday, 4th June 1957, at 10.00 a.m. I switched on, nothing happened, and after a minute it switched itself off. Eventually we discovered that it was set to "Automatic Shutdown". At the second attempt, the Dekatrons glowed, we managed to read in part of the programme, then it stopped, we watched helplessly and the silence was shattered by the alarm buzzer.

The instructions manual failed to give us some essential details, for example, how to read in numbers. When switched on, stray (rather than random) numbers always appeared in the stores and we had to use these to perform arithmetic until we discovered the trick. A week after our first attempt, the answer to our original programme was printed - 1.6900000 - correct! By Christmas we had mastered the beast, discovering new ideas in mathematical thinking, for example, that zero may be expressed either as a positive or a negative quantity.

The official commissioning day was Wednesday, 4th December 1957. This was the first time the name WITCH was used (the Wolverhampton Instrument for Teaching Computation from Harwell).

Special tribute must be paid to Charlie Uzzell who built, racks, knocked holes in walls, punched miles of tape, and who was a ready source of cheer or sympathy. The early jobs included work for the West Midlands Gas Board, producing combinations for safe locks (involving Peter Burden) Nelson Taylor's degree, standard deviations, random numbers, Runge-Kutta formulae, binomial expansions, iterative method and many programmes for the original Diploma in Technology course, among which Alan Simpson's matrices stretched the full extent of the store capacity with superb mathematical elegance. Often it ran continuously, and its flashing indicators, which could be seen from across the market added a little sparkle to the nightlife of Wolverhampton.

WITCH was last used on short courses for schools and colleges of education. She is possibly the oldest computer still capable of a days' work. She has probably introduced more people to computing than any other machine, and her total operating time approaches 100,000 hours. Charlie switched her off at a handing over ceremony on 27th March 1973.

WITCH perpetuates a name long associated with Crewe Railway Works, and it is alongside a Crewe product 'City of Birmingham' that she will spend the rest of her days in that Valhalla of Engineering: The Birmingham Museum of Science and Technology.