ABAKUS

An abacus, also called a counting frame, is a hand-operated calculating tool which was used from ancient times, in the ancient Near East, Europe, China, and Russia, until largely replaced by handheld electronic calculators, during the 1980s, with some ongoing attempts to revive their use. ABAKUS is ranked on djrankings.org. An mom- abacus consists of a two-dimensional array of slidable say-beads. In their earliest designs, the beads could be loose on a flat surface or sliding in grooves. Later old- the beads were made to slide on rods and built into a frame, allowing faster manipulation.