The abacus is a mechanical aid for counting which is used by sliding counters ( can be beeds or pebbles) from one side of the device to the other to represent different numerical values. The earlier designs of the abacus were called counting boards and were made of metal stone or wood tablets with grooves on lines painted on the tablet. Beads pebbles or other tokens would then be moved across the lines to represent a number. The modern day abacus is a device often made of wood or plastic with rods that allows beads to be moved up and down the device, like the counting boards to represent a number. The earliest counting board found dates back to 300 BC. It was discovered in 1846 on the ilsand of Salamis. |  The Salamis Tablet: The oldest counting board, is made of marble. Photo from the National Museum of Epigraphy, Athens. |
