## Math in Computing## Early Counting and Calculating Devices |

## What are the oldest surviving counting boards? |

To date, the oldest surviving counting board is the Salamis tablet. Discovered in 1846 on the island of Salamis, it was once thought to be a gaming board, but historians have since determined that the white marble slab was actually used to count items. The tablet, which measures 59 inches (149 centimeters) in length, 30 inches (75 centimeters) in width, and is 1.8 inches (4.5 centimeters) thick, was used by the Babylonians around 300 B.C.E. It contains five groups of markings, with a set of five parallel lines equally divided by a vertical line in the center; below that is a group of 11 parallel lines, all divided by a perpendicular line.

But this was not the only counting board of that time. After the Salamis tablet was developed, the Romans brought out the Calculi and the hand-abacus around 300 B.C.E. to 500 C.E. These counting boards were made of stone and metal. One example of a Roman abacus had eight long and eight short grooves arranged in a row; beads would slide into the grooves, indicating the counted units. The longer grooves were marked I to indicate single units, X to indicate tens, and so on up to millions; the shorter grooves were used to indicate multiples of five (five units, five tens, and so on). There were also shorter grooves on the right side of the abacus, which were probably used to indicate Roman ounces and for certain weight measurements.