Reboot the ole "WITCH"

"Britain’s Oldest Working Computer Roars to Life"

by

Priya Ganapati

September 4th, 2009

Wired

The oldest original working computer in the U.K., which has been in storage for nearly 30 years, is getting restored to its former glory.

The Harwell computer, also known as WITCH, is getting a second lease on life at the National Museum of Computing at Bletchley Park. The machine is the oldest surviving computer whose programs, as well as data, are stored electronically, according to the museum.

The Harwell WITCH is a relay-based machine that used 900 Dekatron gas-filled tubes, each of which could hold a single digit in memory. It has paper tape for both data input and program storage. The computer was used in the design of Britain’s first nuclear reactors.

“Its promises for reliability over speed were certainly met – it was definitely the tortoise in the tortoise and the hare fable,” says Kevin Murrell, a director and trustee of The National Museum of Computing. “In a race with a human mathematician using a mechanical calculator, the human kept pace for 30 minutes, but then had to retire exhausted as the machine carried on remorselessly. The machine once ran for ten days unattended over a Christmas and New Year holiday period.”

It was a feat for its time. Harwell was operational until 1957 and was then used in computer education until 1973. After that it was disassembled and put in storage–only to be revived now.

The Harwell will be housed alongside the rebuild of the earlier, code-breaking Colossus Mark II, the world’s first electronic computer.