1951 digital computer restored and rebooted


This is the Harwell Dekatron, aka Wolverhampton Instrument for Teaching Computation (WITCH), a 61-year-old machine that was rebooted yesterday to become "the world's oldest original working digital computer." Originally operated at the Harwell Atomic Energy Research Establishment, it was moved in 1957 to Wolverhampton's Staffordshire Technical College where it was dubbed the WITCH. There it stayed until retirement in 1973 when it became a museum display before dismantling for storage. In 2008, the National Museum of Computing in Bletchley Park began to restore the valve-laden beast. "The world's oldest original working digital computer"


  1. The name “Harwell Dekatron” desperately cries out for use in some overblown space opera.

    “Captain Harwell Dekatron”.  Gives me shivers.

      1. Bah. Just have to apply a special patch and you get better settings. Fog goes up to .05, and you get playable frame-rates.

        *Some Geomatries may be simplified. Only works in 256 color mode.

  2. I can almost picture the original scientists looking at that thing in amazement, dreaming all kinds of incredible possibilities!

  3. The Dekatron is a decimal counting tube that sends a neon plasma ball in a circle as it counts. There are hundreds of them in this machine, as you can see, to make up the 90 storage words.  The ENIAC had a module with 22 tubes to do more-or-less the same work as one Dekatron tube. Consequently, it had tens of thousands of tubes. 

    Both ENIAC and WITCH are essentially electronic versions of the old rotating-wheel adding machines, with a control unit to make them not require human operators.

    Later on, HP and Beckman made decimal counting modules using four guitar-amplifier type tubes for their frequency counters. By that time, computers no longer used counters but instead did binary math directly with logic adder circuits.

  4. Missed opportunity for someone to reboot it with an oversize double-throw knife switch on the wall while cackling maniacally.  If you’re gonna do it, do it right.

    1. Spoken like a true mad-genius! 

      Not sure what wuld be more appropriate music. Powerhouse, or something a little more classic.

  5. I heard it was pretty awkward when they booted it up in front of all those people, and the desktop picture was vintage porn. Or, as it was known at the time, porn.

    1. After waiting half an hour for the Teletype to print out text art of a half-naked lady sitting on a stool, the audience left in disgust.

  6. Lets see…
      – Clattery bits, lots of them: check
      – Blinkenlites, lots of them: check
      – Not just punchcards, but punchtape: check
      – Analog gauges: check

    Best digital computer ever.

  7. “Well, sure, the Harwell Dekatron looks impressive, don’t touch it, but I predict that within 100 years, computers will be twice as powerful, 10,000 times larger, and so expensive that only the five richest kings of Europe will own them.

    “Could it be used for dating?”

    “Well, theoretically, yes. But the computer matches would be so perfect as to eliminate the thrill of romantic conquest.”

  8. The currently most elderly living person’s fingers are “the world’s oldest original working digital computer.”

  9. In other news, 4,000 extra tons of coal were burned in powerplants nationwide to provide power for an ancient machine known as  the Harwell Dekatron. Global temperatures are expected to rise faster, a UN spokesperson said.

  10. It is not possible to reboot this machine because it doesn’t use a bootstrap loader.  It doesn’t even use an operating system.  All programs are stored on paper tape.

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