The earliest mechanical mathematical devices were crude, slow, and subject to errors. Users had to adjust the device manually for some functions, such as carrying in addition, just as did the counting table and abacus. The ability to build faster and more accurate devices was constrained by the limited technology of the time.

Schickards's Mechanical Calculator

For many years the French mathematician and philosopher Blaise Pascal (1623–1662) was believed to have built the first mechanical calculator. However, research in the 1950s and 1960s revealed that an earlier mechanical calculator was built by Wilhelm Schickard (1592–1635), a German professor and minister.

Schickard also had an interest in mathematics, and was a friend of Johann Kepler (1571–1630), the prominent astronomer. By 1623 Schickard had produced the first workable mechanical adding machine capable of carrying and borrowing from one column to the next. The machine consisted of a set of Napier's...