Slow, but tireless
WITCH computed in the decimal system and used gas-filled Dekatron tubes for memory, which glow orange while it works. A single calculation could take it several seconds, so a person with a mechanical calculator could keep pace with it. Unlike a person, though, it could keep calculating for days on end without a break and without errors.
From school to storage
Once nuclear scientists got faster computers, a technical college in Wolverhampton won the machine in a competition in 1957, and its students used it to learn programming. That's when it got the name WITCH. It later stood in a museum, then spent years sitting in storage, until volunteers from The National Museum of Computing spent three years restoring it.
Where to see it
The computer now runs at The National Museum of Computing in Bletchley Park, where Alan Turing worked during the war. Nearby is also a reconstruction of the Colossus codebreaking machine. Compared with today's phones, WITCH is a billion times slower — but it shows that well-built electronics can last for decades.