Led by electrical engineer Vannevar Bush, a team of scientists at the Massachusetts Institute of Technology, USA, began working on a "differential analyser" in 1930. Put into use a year later, Bush's machine, an important step above mechanical adding machines, was the first modern analog computer, and the ancestor of electronic calculators.

Bush's device was very different from today's fast, silent and compact computers. It covered several hundred square feet of floor space at MIT and was made of hundreds of rotating steel rods that simulated numerical operations. Instead of a keyboard, screwdrivers and hammers were used to run it. Although primitive, the device could solve lengthy sets of differential equations and handle up to 18 variables at a time.

The next generation of computers, developed during World War II, used electronic technology rather than Bush's electro-mechanical methods. Eventually, the development of transistors, solid circuitry, and the microchip led to even smaller, faster and more powerful machines.

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