1) ABACUS
Abacus is a calculating device invented by the Chinese 3000 years ago. This device is mainly used to perform simple arithmetic operations. Abacus had movable beads fixed on the wires and this was used for arithmetic calculations especially for finding value notation. The digits are represented by beads of counters.
REPRESENTATION OF DECIMAL SYSTEM
In Abacus beads was used for representation of decimal system. The beads on the rightmost wire represent ones, the next neighboring wire represents tens and the next neighboring wire represents hundreds.
Arithmetic calculations such as addition or subtraction can be performed by moving the beads sideways. Each row represents a value and in the same way, each position of the bead also represents a value.