Building the Analytical Engine

December 25, 2010

Most of us, when we think about the early development of computers, probably think of early electronic machines like the ENIAC, built originally at the University of Pennsylvania for the US Army Ballistics Research Laboratory (but also used by John von Neuman for the hydrogen bomb project at Los Alamos), or perhaps the ACE computer, built at the National Physical Laboratory in the UK from a design by Alan Turing.

Arguably, though, the first design for a stored program computer was developed about 100 years earlier, by the British mathematician, Charles Babbage.  The device Babbage designed, the Analytical Engine, was never built, but it seems clear from the design that it would have been the world’s first Turing-complete computer (meaning it could compute any computable function), incorporating features commonplace in computers today, including sequential control, branching, and looping.  Only a trial model, on display at the Science Museum in London, was built in Babbage’s lifetime.   Lord Byron’s daughter Ada, Lady Lovelace, for whom the Ada programming language is named, wrote a program for the Analytical Engine to compute Bernoulli numbers, and was possibly the world’s first programmer.  Babbage’s son Henry built a portion of the machine, the Mill (essentially, the CPU), in 1910; that machine is also on display at the Science Museum.

Now the New Scientist site reports that  the British writer John Graham-Cumming has launched a project to build a working Analytical Engine from Babbage’s design; he is hoping to raise £100,000 in donations to fund the project.

I have started a project to build an analytical engine, dubbed Plan 28 after one of Babbage’s detailed plans. I’m aiming for £100,000 and hope to complete the project in time for the 150th anniversary of Babbage’s death on 18 October 2021.

At one time, it was thought that building the Analytical Engine would have been impossible in Babbage’s time, because it would require manufacturing precision that would not have been possible.  However, the Science Museum built a working model of one of Babbage’s simpler machines, the Difference Engine No. 2, with tolerances that were achievable at the time, so there is a good chance that a working Analytical Engine could be built as well.

Of course, we won’t really know until someone tries; but I find the idea of a fully-functional, steam-powered mechanical computer to be just really fascinating.

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