Charles Xavier Thomas de Colmar (1785 – 1870) was a French inventor and entrepreneur. While serving in the French army, he was inspired to create a more practical calculating machine. In 1820, he patented a machine based on Leibniz’s Stepped Reckoner.
The Arithmometer was the first commercially successful and mass-produced mechanical calculator, remaining in production for over 90 years. Its reliability and ease of use made it the first calculating machine to be widely adopted in offices and businesses, marking a major step in the commercialisation of computation.