2013: Advent Computing: A historical divergence: Wartime advances

by on December 11, 2013

The key idea from Babbage’s analytical engine was that of a single computer which could solve multiple problems. Previous devices were built to solve a single problem, and at best would need to be disassembled and rearranged before they could be used for anything else. More likely, they’d need to be completely re-engineered.

Still, it wasn’t until the 1930s that significant progress was made.

At least in Britain, we tend to hear more about the work of Alan Turing during WWII, but his work was preceded by others. Specifically, Konrad Zuse, a German, worked on a series of calculators to assist his tedious engineering calculations.

Zuse’s first calculator, the Z1, was a relatively simple mechanical calculator built in 1938. Although it was programmable using a punch card, it was only capable of very limited use.

By 1939, Zuse’s Z2 was electromechanical (it used electricity to control mechanical switches) and gained him funding from the Nazi government. The Z3 was presented in 1941 to the Deutsche Versuchsanstalt für Luftfahrt (“German Laboratory for Aviation”), and was the first programmable and fully automatic digital computer. It missed one vital component of modern programmable computers: it had no “conditional branching”, so it could not choose between different operations depending on some intermediate part of the calculation.

A black-and-white photograph of two women operating a large computer. The computer has two large sections, both taler than the women, with a control panel visible in the left one, vacuum tubes visible on both, and a large paper tape reel on the right of the machine.

Colossus in use

On the Allies’ side, decrypting German messages led, via Rejewski’s bomba and Turing’s bombe (neither of which were programmable), to Colossus. Designed by Tommy Flowers and put to work in 1944, it was the first fully electronic programmable computer – rather than using mechanical switches, it used considerably faster “thermionic valves” or “vacuum tubes” for memory.

Meanwhile, across the pond, the US Army was working on ENIAC. ENIAC is the point at which computers really start resembling modern devices: unlike Colossus (and a selection of others I’ve skipped over), ENIAC was general purpose. Although the initial motivation for building it was ballistics tables, it was designed to be put to any job. Notably, it was the first electric computer that could do anything a Turing machine could.

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