Invented: Around 500B.C.
Abacus was an important counting machine invented in ancient time.
It was capable of performing operations like addition, substraction, division and multiplication.
In ancient time it was widely used in Babylon, China and throughout Europe until the middle ages.
How it worked?
In Abacus the beads represented the columns.
The right-most column represented the unit, the next for ten and so on.
Numbers were represented by moving beads at appropriate column.
In Japan this instruments is known as SOROBAN.
Abacus was used to perform simple addition and subtraction.
Abacus can be used by visually impaired people (or students) who cannot use calculator to perform calculations.