Abacus

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Abacus

An instrument allowing one to quickly add and subtract numbers. Generally, an abacus is composed of a rectangular frame in which horizontal rods are partially covered with beads. The beads may be moved one way or the other to make calculations. It was invented in China in the 2nd century CE and is considered the earliest calculator.
References in periodicals archive ?
(6) Many writers use the term "abbacus" or "abacus" instead of "abbaco" when referring to these vernacular schools, presumably because the abacus was used in these schools when they first began to appear in 13th century Italy.
van Egmond (1980) Practical Mathematics in the Italian Renaissance: A Catalog of Italian Abbacus Manuscripts and Printed Books to 1660, Firenze: Istituto e Museo di Storia della Scienza.