The abacus is a mechanical aid used to perform arithmetic calculations (sometimes called bead arithmetic). It is believed that the counting board, ancestor of the abacus, first appeared around 3000 B.C. as an arrangement of sand and pebbles and was developed over the next 4,500 years into the modern abacus. Such devices evolved from the need to count things without having to remember what was counted. For example, merchants needed a way to count goods bought and sold and to preserve these figures. The abacus and kindred devices functioned efficiently in this capacity until paper and pencil became commonly available (and even after, in some parts of the world). The abacus is considered by many to be the ancestor of the calculating machine and the computer.

The evolution of the abacus is often divided into three periods: ancient times, Middle Ages, and modern times. The earliest counting boards, dating...