An abacus, also called a counting frame, is a calculating tool used primarily by Asians for performing arithmetic processes. Today, abaci are often constructed as a wooden frame with beads sliding on wires, but 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 China, Japan, Africa, India and elsewhere. - Wikipedia