An abacus is a counting device that uses beads on a table or string that represent numbers. The device is divided into columns, each column representing a multiple of 10 (x10, x100, x1000 etc.) and each column has 10 beads in it. This enables numbers to be formed by rearranging the beads, this means that simple and complex arithmetic can be performed on the abacus.
The abacus was invented around 2,700-2,300 BCE, by the Sumerians (Mesopotamia) ; that makes the invention about 4,400 years old. This is the oldest dated abacus, there are several versions between 2,700 - 1,000 BCE, with many groups claiming responsibility for the invention.
The earliest know Chinese abacus, called the Saunpan (translated as Counting tray) is only dated to about 200 BCE.