An abacus (or soroban in Japan)
China invented the abacus .
disadvantage of abacus
who discover abacus
The Chinese abacus
An Abacus has beads and strings.
How did the abacus occur?
The First appearance of an abacus was in Sumeria around 2700 to 2300 BC.
Abacus is the first counting machine!
the Chinese invented the abacus