Thomas de Colmar's Arithmometer, c 1890.
© Science Museum / Science & Society Picture Library
Charles X Thomas de Colmar invented his Arithmometer in 1820. In the 1860s it became the first commercially succesful calculating machine and could be used for addition, subtraction, division and mulitiplication. The mechanism was based on the stepped reckoner invented by Liebniz (1646-1716). Machines of this type were made well into the 20th century.