From Wikibooks

The Abacus is the oldest of math tools that is still used in most places. The Abacus was made by ancient people that made better the knowledge of the use of the abacus to better their learning in time and construction.

The Abacus was once the only math tool and is considered a computer in thought. The use of a Abacus can be as good as a use of a modern math tool, in good hands though. In the hands of an expert, the abacus can beat a hand math tool at any math except for that of division.