The abacus is a simple counting device of ancient (probably Mesopotamian) origin. It has moveable balls placed on poles, wires or grooves. The positions of balls on each pole represent numbers and the poles themselves represent place values. Therefore, the highest value a six-line-abacus is capable of representing is 999,999. Additions and subtractions are quite easy to perform with the abacus, however, multiplications and divisions present some difficulties. One of the advantages of the abacus is its ability to serve as a counting device for the illiterate.

The earliest way of counting involved drawing lines simply in the sand. Herodotus mentioned that the ancient Egyptians had used abacus. The lines would represent the 1st, 10s 100s, etc. the spaces between them would represent the units 5s, 50s, 500s, and so on. Placing pebbles between those lines as place holders were representing the numbers. Dust-covered tables were used for this purpose as well.

In certain parts of the world, the abacus is still in everyday use for business purposes. In the 1980s, the traditional 10-ball version was still widely used in the Soviet Union: although the stores had electronic cash registers, the cashier would first use the abacus to calculate (amazingly fast) the total price, then enter this into the register. The abacus was also used by waiters, as well as stewardesses selling souvenirs on airplanes. In Hungary, after a few decades of pause, it is being used again in primary schools. At the beginning of the 1960s, a large abacus used to stand in the corner of every classroom (the simplest type with 10 balls per row). In recent years however, kids have been using the Japanese equivalent of the abacus, the 4+1-ball soroban to learn counting.

We must not underestimate the effectiveness of the abacus. On the 12th of November, 1946, a contest took place between the Japanese Macuzaki who used a soroban and the American Wood, who worked with an electromechanical calculator. They had to solve the same counting tasks. It was Macuzaki who finished each task earlier.