Stepped Reckoner

The Stepped Reckoner, also called the Leibniz calculator, was a mechanical calculator that the German mathematician Gottfried Wilhelm Leibniz began building in 1673 and completed in 1694. It was the first calculator able to perform all four basic arithmetic operations directly, using a stepped cylinder gear, later called the Leibniz wheel, to add or subtract an eight digit number to or from a sixteen digit number and to multiply and divide through repeated addition and subtraction. Manufacturing precision problems and a flaw in its carry mechanism meant only two prototypes were ever built and neither worked fully reliably, but the stepped cylinder design itself remained in use in calculating machines, including the Curta, for roughly two hundred years.