Roman abacus

The Roman hand abacus was one of the earliest known portable calculating devices, used in the Roman world for practical arithmetic. It was a portable base-10 form of the abacus, a calculating aid with earlier western antecedents in Greek counter-based reckoning. Its movable beads represented values in decimal place-value columns, allowing calculations to be carried out on the device while Roman numerals were used mainly to record results. The device also included positions for fractional values used in Roman measures and Roman currency, especially the uncia, or one-twelfth of a unit.

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