Math in Computing

Early Counting and Calculating Devices

What is an abacus?

An abacus (the plural being either abacuses or abaci) is one of the earliest counting devices. The term comes from a Latin word with origins in the Greek words abax or abakon, meaning “tablet” or “table”; these words probably originated with the Semitic word abq, or “sand.” The devices—originally made from wood but now usually including plastic—perform arithmetic functions by manually sliding counters (usually beads or discs) on rods or wires.


The Salamis tablet, discovered in 1846, is the oldest surviving counting board. It was used by the Babylonians around 300 B.C.E.

Contrary to popular belief, abaci were not truly calculators in the sense of the word today. They were used only as mechanical aids for counting. The calculations were done inside the user’s head, with the abacus helping the person keep track of sums, subtractions, and carrying and borrowing numbers. (For more about carrying and borrowing in arithmetic, see “Math Basics.”)


This is a web preview of the "The Handy Math Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App