The abacus
(plural abaci or abacuses), also called a counting frame, is a
calculating tool that was in use in Europe, China and Russia, centuries
before the adoption of the written Hindu–Arabic numeral system and is
still used by merchants, traders and clerks in some parts of Eastern
Europe, Russia, China and Africa.
Abacus - Wikipedia
https://en.wikipedia.org/wiki/Abacus
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