## -3,000 – abacus

An abacus is a counting device, usually constructed as a frame with beads sliding on either wires or slender rods. The beads represent quantities of numbers and each successive row of beads can represent a different place in a numbering system. In the decimal system, the first row of beads would be “1s” and the next row would be “10s” and the next row “100s” and so on.

They often had four beads for counting from one to four on the bottom section of the abacus and a “heaven” bead above that represented five of the quantity below. This allowed for counting to four with the bottom beads, then resetting the bottom to zero and moving the top bead into the “five” position, then adding more bottom beads to yield six through nine and eventually resetting all the beads to zero as the quantity ten would be moved over to the next row as a “one”.

The abacus probably evolved from a counting system that first used pebbles or some other small object placed in depressions in sand and then the same small objects placed in depressions carved into a “counting board”.

It is possible to do multiplication and division on an abacus once the correct methods are understood.