The history of warfare has been a history of data as well as of violence - knowing your enemies' movements and plans has always been vital; keeping track of supplies and reinforcements crucial. But the Second World War was a conflict where the ability to use machines to crunch numbers proved decisive, as Mike Richards explains.

If you had asked to see 'a computer' before the outbreak of the Second World War, you might well have been taken to see a person who calculated numbers. Many businesses would use mechanical calculators operated by a hand crank; and the very largest may have used an electromechanical calculator in which information was stored on punched paper cards. The electronic computer was restricted to the pages of science fiction comics; but the foundations for the modern computer age were already laid.

As early as 1822, the British mathematician Charles Babbage had realised that the mechanical technologies of the Industrial Revolution could not only mass-produce physical items such as cloth or steel, but also process information. Babbage conceived his Difference Engine – a colossal construction of gears and switches that would generate mathematical tables with unparalleled precision. He never completed his Difference Engine (although a working replica now sits in the Science Museum), having devised a second revolutionary machine, the Analytical Engine.

Babbage’s Difference Engine was designed to complete a single task; but the Analytical Engine would perform any mathematical operation. In many ways it was the ancestor of all modern computers. Babbage’s machine would receive its instructions (what we would call a program) and information (data) on thousands of punched cards. Babbage’s steam-powered machine would have been the size of a house and composed of thousands of gears but its operation would have been remarkably similar to the modern computer!

The remainder of the 19th and early part of the 20th Centuries saw huge improvements in mechanical calculators, but crucially they were all restricted to performing a tiny range of tasks – such as adding, subtracting or multiplying numbers. None of these machines could be programmed to perform a new operation; if you owned a calculator that did not calculate fractions there was no way of adding that functionality – you would need to go and buy a new calculator that could process fractional values.

The computing revolution was unleashed in 1937 by the British mathematician Alan Turing. Turing was exploring the mathematical concept that there are certain logical questions that cannot be answered and was discussing ways in which the unanswerable questions could be identified.

Turing’s paper On Computable Numbers included a discussion of an imaginary machine capable of performing a simple mathematical task (say adding two numbers) by following precise, logical steps. Different Turing Machines would be built for performing different tasks. To perform a particular task, (say adding two numbers, multiplying the result by a third number and dividing that result by the fourth), a series of Turing Machines would be joined together in the necessary order – just like a child’s building blocks.

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