Abacus

History of the Abacus. An abacus helps make arithmetic calculations. It is composed of beads strung on parallel wires in a rectangular frame. In ancient times it was composed of a row of grooves in sand into which pebbles were placed. Later, the use of a slate or a board made it a portable device. Each bead's value is determined by its position. One bead on a wire has the value of 1; two together have the value of 2. A bead on the next wire has a value of 10, and a bead on the third wire has a value of 100. The links included herein relate to the abacus.