TONY CRADDOCK / SCIENCE PHOTO LIBRARY TONY CRADDOCK / SCIENCE PHOTO LIBRARY
Abacus. The abacus is an early form of arithmetic calculator. Its name is derived from a method of counting using stones on a 'flat surface' (= abacus, Latin) familiar to the ancient Greeks and Romans. The modern abacus consists of beads on a frame, known as a soroban in Japan and a shchoty in Russia. Experienced users may perform calculations faster than by using an electronic calculator, but the technique needs practice.
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