An abacus is a calculating tool that was used in ancient times and is still used today in some parts of the world. The abacus consists of a frame with rods on which beads are strung. The beads are moved around to perform mathematical calculations.

The use of the abacus can be traced back to ancient Sumeria, where it was used for counting sheep and other animals. In China, the first recorded use of the abacus dates back to the 2nd century BC. During the Tang Dynasty (618-907), Chinese mathematicians developed algorithms for performing arithmetic operations using an abacus with nine columns of beads, known as a suanpan.

Today, there are different types of abacuses around the world, including Japanese soroban and Russian schotyka. While electronic calculators have replaced the need for most people to know how to use an abacus, many still find it helpful in doing mental calculations or teaching math concepts such as place value and addition/subtraction strategies.