Pascal's calculator

Pascal's calculator, also called the Pascaline, is a mechanical calculating machine that the French mathematician Blaise Pascal invented in 1642 at the age of eighteen to help his father, a tax supervisor in Rouen, with arithmetic. It used spoked metal wheels marked with the digits zero through nine, turned with a stylus, and carried digits between wheels through a gravity driven mechanism called the sautoir. Pascal built around twenty machines over the following decade under a 1649 royal privilege that gave him exclusive manufacturing rights in France, and it is remembered as the only operational mechanical calculator built in the seventeenth century; nine machines survive today in European museums.