Charles Xavier Thomas de Colmar invented the first calculating machine to be produced in large numbers. This invention came about in France in 1820 as part of a national competition and the machine was called the Arithmometer.

Thomas de Colmar was serving in the French army (during the Spanish and Portuguese campaigns of 1809-1813) as a military administrator when he had the idea of the Arithmometer. In 1820 he developed a prototype and had it patented. This patenting and all subsequent work on the Arithmometer was carried out after de Colmar left the army and started work in the relatively new field of insurance. There is little evidence that working versions of the Arithmometer were produced at this time; it is not until 1840 that we find proof of their manufacture. The Arithmometer was essentially an early and large version of a pocket calculator (occupying the best part of a desk...