Arithmometer

The arithmometer was a mechanical calculator invented by the French engineer Thomas de Colmar, who began developing it in 1818 while serving in the French military and patented it in November 1820. Operated by a crank and a system of movable sliders, it could add, subtract, multiply and divide, and became the first digital mechanical calculator sturdy and reliable enough for daily office use, though commercial manufacturing did not begin until 1851. Around 5,500 arithmometers were produced between 1851 and 1915, and its design set the pattern that roughly twenty other European manufacturers followed, making it the first mechanical calculator to see genuinely widespread commercial and office use.