abacus

An abacus is a calculating tool that predates modern arithmetic devices. It consists of a rectangular frame with rods, on which beads slide to represent digits. Each rod corresponds to a place value, and moving beads toward a central reckoning bar indicates units to be counted. The arrangement of beads varies by culture: the Chinese suanpan typically has two beads on the upper deck and five on the lower deck per rod, while the Japanese soroban uses one bead on the upper part and four on the lower part. Some European and Russian variants use different layouts, but the underlying principle remains the same.

Originating in ancient times, the abacus developed independently in several regions and remained a fundamental computational tool long after written numerals and paper arithmetic appeared. It was used by merchants, traders, and scholars for addition, subtraction, multiplication, division, and, in some variants, more complex operations such as square roots. The device does not perform automatic calculation; users input values by manipulating beads according to established operational rules.

With the rise of mechanical and electronic calculators, the abacus declined in daily use in many areas, but it persists in education as a method to teach place value and arithmetic concepts and is still used in some cultures for traditional reasons. Modern practitioners also employ abaci for mental calculation, a skill known as abacus-based mental calculation.