November 21st, 2012 by Alan Weissberger
After a three-year restoration project at The National Museum of Computing, the Harwell Dekatron (aka WITCH) computer was rebooted on 20 November 2012 to become the world’s oldest original working digital computer. Now in its seventh decade and in its fifth home, the computer with its flashing lights and clattering printers and readers provides an awe-inspiring display for visiting school groups and the general public keen to learn about our rich computer heritage.
The computer, originally called Harwell but now called the Wolverhampton Instrument for Teaching Computing from Harwell (WITCH), was originally powered up in 1951. The WITCH only stores numbers and reads data from punched paper tape. Doesn’t that sound archaic? Not in 1968!
Personal Note: On my 2nd programming job (May to Dec 1968), I had to manually set 2 position switches to bootstrap the Raytheon 703 minicomputer, then use paper tape to load various programs, e.g assembler, compiler, etc. It was a real hassle! I successfully wrote the magnetic tape driver program and then a real time program to test integrated circuits, using the Raytheon Automated Test System (RATS). After the mag tape I/O driver was operational, we could use it to load stored programs into core memory where they were then executed.