In 1642, when he was about nineteen, Blaise Pascal built a calculating machine to help his father, a tax official in Normandy, with long columns of arithmetic. The device - later called the Pascaline - used a row of geared wheels, each marked with digits, that the operator turned with a stylus to enter numbers. Its key innovation was a mechanism Pascal called the sautoir, which automatically performed the carry from one digit to the next when a wheel passed nine, so that addition and subtraction propagated correctly without the user having to manage carries by hand.
Because the machine was built for French money of the day, its wheels were not all base ten: some had twenty teeth for sols and twelve for deniers, matching the units of livres, sols, and deniers. Pascal built and revised several examples over the following years and was granted a royal privilege for the design in 1649. Only about a dozen original Pascalines survive; the Musee des Arts et Metiers in Paris holds several, including one dated 1652.
The Pascaline was not the first attempt at a calculating machine, but it was an early one that actually worked and that Pascal produced in quantity, and it proved that arithmetic could be embodied in gears. It is a direct ancestor of Leibniz’s stepped reckoner and, two centuries later, of Babbage’s engines.