The abacus was initially used for arithmetic tasks. The Roman abacus was used in Babylonia as early as <answer>2400 BC</answer>. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money.
When was the Roman abacus first used?
2400 BC