Color enhance woodcut image from Ain new geordnet Rechenb, chlein auf den linien mit Rechenpfenningen (An ordered new computing booklet on the lines with computing pennies) by Jacob K'bel, 1516. An abacus is a counting device that consists of a frame holding rods on which a specific number of beads are free to move. Each rod designates a given denomination (units, tens, hundreds, etc) in the decimal system, and each bead represents a digit or a specific number of digits. Originally they were beans or stones moved in grooves in sand or on tablets of wood, stone, or metal. The abacus was in use centuries before the adoption of the written modern numeral system and is still widely used by merchants, traders and clerks in Asia, Africa, and elsewhere. The user of an abacus is called an abacist.