The modern abacus was first used in China around 2nd BC. The Chinese abacus, known as the Suanpan “Counting tray”, Mandarin suàn pán, Cantonese syun3 pun4), is typically 20 cm (8 in) tall and comes in various widths depending on the operator. It usually has more than seven rods.
The beads are usually rounded and made of a hardwood. The beads are counted by moving them up or down towards the beam. If you move them toward the beam, you count their value. If you move away, you don’t count their value.
The abacus is a computing device on which arithmetic calculations are performed by sliding counters (beads, pebbles, or flat discs) along rods, wires or lines. The instrument may have originated in the Middle East before the time of Christ. Small stones known as calculi, from the Greek khalix, pebble, were moved along lines drawn in stone or sand. Our modern terms “calculate” and “calculus” come from the term calculi, while the word “abacus” comes from a Greek word meaning a board or slab, or a calculating table.