Re-launched one of the oldest digital computers – Harwell WITCH

The oldest, but still, as it turned out, the current computer turned 61 years old. This rather unusual exhibit was on display at the British National Museum of Computing Technology. The original name of the device – Harwell, but now it is called the Wolverhampton Instrument for Teaching Computing from Harwell or reduced WITCH. It was first launched in 1951. From 1952 to 1957 the machine was used in early atomic research, and then was sent to the University of Wolverhampton, where it served until 1973. From 1973 to 1997, the computer played the role of an exhibit at the Birmingham Museum (UK), and then was buried in the vault until 2009. Three years later, WITCH was restored and renovated and is now on display at Bletchley Park, where during the Second World War, was located the main unit cryptographic UK.

WITCH Harwell Oldest Digital Computer
By modern standards – it is very primitive and monstrously huge computer, data entry which is produced using tape, and they were stored in volatile memory. For computing activities it used the relay, and to output data – a teletype or tape. The most interesting part of the venerable mega computer is volatile memory that is based on decatrons (multi-electrode discharge lamp, cold cathode). Because of them, the device used the decimal number system, not binary, as in modern computers.


WITCH has 40 banks on 8 decatrons each, that is, the computer is able to store up to 40 eight-digit numbers. The very process of calculations using the relay lasted very long – the multiplication of two numbers takes about 5-10 seconds. This is not a supercomputer, however, in contrast to the man it is not at fault and is capable of operating days without operator intervention. Jack Howlett, who worked with WITCH in 50 years, recalled a record 10 days of non-stop work computer during the Christmas holidays, “We left him a lot of miles on the input data tape, which should be enough for about ten days, and when returned – the computer is still ticking. ”

This was all regarding the oldest computers called Harwell or WITCH.

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