An abacus is an ancient tool used for counting, consisting of a framed set with rods on which balls or beads are moved. The abacus has been in existence in China since the second century BCE, although ...

The abacus, a simple counting aid, may have been invented in Babylonia (now Iraq) in the fourth century B.C. The Antikythera mechanism, used for registering and predicting the motion of the stars ...