Leibniz calculating machine, 1694.
© Science Museum / Science & Society Picture Library
Detail. Gottfried Leibniz (1646-1716), German mathematician and philosopher, conceived the idea of a machine that could multiply by repeated addition. He constructed the first model in 1694, the important feature of this early calculating machine was the stepped reckoner. Leibniz published his system of infinitesimal calculus in 1684, sparking controversy when Newton published his in 1687.