Arithmometer
The Arithmometer or Arithmomètre was the first digital mechanical calculator strong enough and reliable enough to be used daily in an office environment. This calculator could add and subtract two numbers directly and could perform long multiplications and divisions effectively by using a movable accumulator for the result. Patented in France by Thomas de Colmar in 1820 and manufactured from 1851 to 1915, it became the first commercially successful mechanical calculator. Its sturdy design gave it a strong reputation of reliability and accuracy and made it a key player in the move from human computers to calculating machines that took place during the second half of the 19th century.
