Abacus, also called a counting frame，is a calculating tool that was in use centuries before the adoption of the modern numeral written system.

While the first documentation of a Chinese abacus has been dated around the 14* century, some forms of the abacus or counting rods have appeared in history as early as 2,700 BC in ancient Samaria ( Sumar, 苏美尔). Mentioned in ancient Roman texts, as well as among Egyptian hieroglyphics( 象形文字)，one example of archaeological evidence of the Roman abacus dates to the first century AD and Greek artifacts dated as early as 500 BC. 

The abacus has survived the centuries with its purpose intact. Most often constructed of a wood frame with beads sliding on wire or wooden pegs, it is still widely used by merchants, traders and clerks in Asia，Africa, and elsewhere.

 The Chinese abacus divides the frame with a horizontal bar. The area above the horizontal bar, heaven, contains two beads per vertical rod; each has a value of one. Each vertical rod represents a unit of ten. Calculating is accomplished by moving beads toward or away from the horizontal divider. In the mid-1800s, the 2/5 abacus was replaced by the 1/5 abacus, and, by the 1930s, the most widely used from of abacus was the Japanese-made soroban(日式算盘)，1/4 abacus.