An ancient calculator consisting of a frame, rods, and beads. A horizontal beam separates the frame into an upper deck and a lower deck, and a place notation is used to represent numbers and calculations by sliding the beads into various positions on the two decks. The abacus illustrated is the Chinese or ‘2/5’ abacus (having 2 beads on each rod on the upper deck and 5 beads on each rod on the lower deck); the Japanese abacus is ‘1/4.’
Although the use of abaci is mostly associated with Asian cultures, they were also used in ancient Roman, Egyptian, Greek, Persian, Mesopotamian, and Mesoamerican civilizations. A skilled abacist can typically perform arithmetical calculations much faster than most people can even when using a modern electronic calculator.