Harwell Computer

The Harwell computer, also known as Harwell Dekatron computer later than Wolverhampton Instrument for Teaching Computing from Harwell ( WITCH ), is a 1951 British mainframe taken into service. After three years of restoration it is operational again since 2012 and thus the oldest still functioning electronic computer in the world. The computer uses relays for the calculator and Zählröhren.

History

Atomic Energy research

The two and a half -ton mainframe computer was from 1949, built for the "Atomic Energy Research Establishment " in Harwell, Oxfordshire. The three developers in the electronics department of Harwell were Edward ( Ted ) Cooke - Yarborough and Robert (Dick) Barnes, who also witnessed the reconstruction of the computer. He went for the first time in 1951 in operation. In 1957 he was retired as obsolete.

Teaching Aids

After a high school competition, the computer came to the " Wolverhampton and Staffordshire Technical College " ( which later became the University of Wolverhampton was ), where it was used until 1973 as a teaching tool in the computer science department. Here, the machine got the name " WITCH " ( German: "witch" ) for " Wolverhampton Instrument for Teaching Computing from Harwell ."

Science and Industry Museum

Discarded as too old for the second time, WITCH came in 1973, " Museum of Science and Industry " in Birmingham. As this museum closed in 1997, WITCH was dismantled and stored until further notice.

National Museum of Computing

Kevin Murrell of the " National Museum of Computing " at Bletchley Park discovered by chance in 2009 parts of the computer on a photo. Under the direction of Delwyn Holroyd the items have been restored and reassembled. On November 20, 2012 WITCH was an interested audience - back into operation - including some of the designers and members of the original operator.

Technical details

The Harwell computer was designed and built by the Electronics Division of the "Atomic Energy Research Establishment ." Its memory consisted initially of 20, later 40 eight-digit Dekatron registers, hence the name " Harwell Dekatron computer " sometimes used. Figures were not binary but decimal stored. The application was submitted via tape, the output via a telex or also on paper tape.

The Harwell computer was not very fast, because the arithmetic unit with relay, ie electro-mechanical worked. It took up to ten seconds to multiply two numbers. In tests it was even a few people to keep for a while when multiplying by the computer step. But he was very reliable and was able to work for days without problems. He was replaced by a transistor-based computer, the Harwell CADET.