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World's oldest working computer gets fired up

Visitors can now check out the fully restored nearly 3-ton WITCH as it lights up The National Museum of Computing with its flashing bulbs and chattering printers.

The WITCH at Wolverhampton -- with serious tape readers. Photo courtesy of Express & Star via The National Museum of Computing

With the advent of smaller, thinner, and lighter devices, it now seems crazy to think of a computer as a room-sized mechanism meant mostly for government use. But that's exactly what a computer was 61 years ago.

Now, visitors can see what the first hardware designers were doing when they created what is currently the world's oldest working digital computer -- the Wolverhampton Instrument for Teaching Computing from Harwell, or WITCH. The more than half-a-century old device has been restored and rebooted at its home in The National Museum of Computing in Buckinghamshire, England.

"In 1951 the Harwell Dekatron was one of perhaps a dozen computers in the world, and since then it has led a charmed life surviving intact while its contemporaries were recycled or destroyed," trustee of the museum Kevin Murrell said in a statement.

Work began three years ago on restoring WITCH, which was first used in 1951 for atomic research. The computer was run on telephone exchange relays and hundreds of Dekatron gas-filled tubes that could each hold a single digit in memory. Paper tape was used to both input data and store the output of the machine.

While on display at the museum, people can see the nearly 3-ton machine's lights flash and its printers rattle. WITCH's design was based on reliability rather than speed. It was meant to solve algorithms at roughly the same speed as a single human mathematician using a mechanical calculator and could work for days on end without an error, according to the museum.

"To see it in action is to watch the inner workings of a computer -- something that is impossible on the machines of today," Murrell said.

The machine is not the oldest electronic calculating device but is regarded as the first modern computer still capable of working. WITCH is on display at the museum alongside the Colossus Mark II, which is the world's first electronic computer.