At it most basic, the abacus is a device used to keep track of numbers, much the way a modern calculator now does. The predecessor to the beaded abacus was called simply the "counting board," and it is thought to originate on the island of Salamis in Greece.
The Device's Origins
The Chinese are thought to have invented the formal abacus around the second century. That device had beads arranged on a frame, allowing the user to slide the beads from one side of the device to the other to count sums. Before that, in about 300 B.C., ancient Greeks fashioned counting boards from metal, stone or even simple lines drawn in the sand. Instead of attached beads like the Chinese version had, the counting board had sets of vertical and horizontal lines, between which people set stones or beads to mark tens, hundreds or thousands. This could have been used to track crops or household goods as well as to calculate how much something should cost.
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