Definition:Abacus

Definition
An abacus (plural: abacuses or abaci) is a tool for performing arithmetical calculations.

It consists of:
 * a series of lines (for example: grooves in sand, or wires on a frame), upon which are:
 * a number of items (for example: pebbles in the grooves, or beads on the wires),

which are manipulated by hand so as to represent numbers.

As such, it is the earliest known machine for mathematics, and can be regarded as the earliest ancestor of the electronic computer.

Also see
Those who perform arithmetical calculations using an abacus are called abacists.

The conventional method of performing arithmetic, that is, by using Arabic numerals, used to be called algorism.