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An abacus is a calculation tool, often constructed as a wooden frame with beads sliding on wires. more...

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It was in use centuries before the adoption of the written Hindu-Arabic numeral system and is still widely used by merchants and clerks in the People's Republic of China, Japan, Africa, and elsewhere.

Origins

The origins of the abacus are disputed, as many different cultures have been known to have used similar tools. It is known to have existed in Babylonia and in China, with invention to have taken place between 1000 BCE and 500 BCE. The first abacus was almost certainly based on a flat stone covered with sand or dust. Lines were drawn in the sand and pebbles used to aid calculations. From this, a variety of abaci were developed; the most popular were based on the bi-quinary system, using a combination of two bases (base-2 and base-5) to represent decimal numbers.

The use of the word abacus dates back to before 1387 when a Middle English work borrowed the word from Latin to describe a sandboard abacus. The Latin word came from abakos, the Greek genitive form of abax (\"calculating-table\"). Because abax also had the sense of \"table sprinkled with sand or dust, used for drawing geometric figures,\" it is speculated by some linguists that the Greek word may be derived from a Semitic root, ābāq, the Hebrew word for \"dust.\" Though details of the transmission are obscure, it may also be derived from the Phoenician word abak, meaning \"sand\". The plural of abacus is abaci.

Babylonian abacus

A tablet found on the island of Salamis (near Greece) in 1846 dates back to the Babylonians of 300 BCE making it the oldest counting board discovered so far. It was originally thought to be a gaming board.

Its construction is a slab of white marble measuring 149 cm in length, 75 cm in width and 4.5 cm thick, on which are 5 groups of markings. In the center of the tablet are a set of 5 parallel lines equally divided by a vertical line, capped with a semi-circle at the intersection of the bottom-most horizontal line and the single vertical line. Below these lines is a wide space with a horizontal crack dividing it. Below this crack is another group of eleven parallel lines, again divided into two sections by a line perpendicular to them but with the semi-circle at the top of the intersection; the third, sixth and ninth of these lines are marked with a cross where they intersect with the vertical line

Roman abacus

The Late Empire Roman abacus shown here in reconstruction contains eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each.

Read more at Wikipedia.org