An abacus is a frame of beads used in China and neighbouring countries for making calculations. A skilled abacus user can produce answers to some calculations almost as quickly as someone using an electronic calculator.

The word abacus is derived from the Latin word abax*,* which means a flat surface, board or tablet. As such, an abacus is a calculating table or tablet. The abacus is the oldest device in history to be used for arithmetic purposes, such as counting. It is typically an open wooden rectangular shape with wooden beads on vertical rods. Each bead can represent a different number. For simple arithmetic purposes, each bead can represent one number. So, as a person moves beads from one side to the other, they would count, 'one, two, three', etc.

An abacus can be used to calculate large numbers, as well. The columns of beads could represent different place values. For example, one column may represent numbers in the hundreds, while another column may represent numbers in the thousands.

One of the most popular kinds of abacuses is the Chinese abacus, also known as the suanpan. Rules on how to use the suanpan have dated all the way back to the 13th century.

On a Chinese abacus, the rod or column to the far right is in the ones place. The one to the left of that is in the tens place, then the hundreds, etc. So, the columns are different place values and the beads are used to represent different numbers within those place values. For addition, beads on the suanpan are moved up towards the beam in the middle. For subtraction, they are moved down towards the bottom or outer edge of the suanpan. The rules of use are a bit more intricate and complicated, but this is the general idea of how one is used.