The abacus is a ancient counting tool that has been used for thousands of years. It was in use in the ancient Near East, Europe, China, and Russia, centuries before the adoption of the written Arabic numeral system. The abacus consists of a wooden frame, rods, and beads. Each bead represents a number, usually 1 or 5, and can be moved along the rods.
In earliest use the rows of beads could be loose on a flat surface, or sliding in grooves. Later the beads were made to slide on rods of some sort built into a frame, allowing faster manipulation. Since counting boards were often made from materials that deteriorated over time, few of them have been found.The oldest counting board that has been found is called the Salamis Tablet. It was found on the island of Salamis, a Greek island, in 1899. It was used by the Babylonians around 300 BC. The exact origin of the abacus is still unknown. Some historians credit the Chinese as the inventors of bead frame abacus, while others believe the Romans introduced the abacus to the Chinese through trade.