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A simple abacus dates back to Mesopotamia 5,000 years ago. The Chinese abacus, designed about 1700 years ago, is made up of rows of beads representing units, tens, hundreds and thousands. It is a rapid tool for adding, subtracting, multiplying and dividing.
The first practical mechanical calculator was made by the Frenchman Blaise Pascal, in 1642, when he was only 19. It had a row of toothed wheels, with numbers around. Numbers to be added or subtracted were dialled in and the answer appeared behind the holes at the top. Modern electronic calculators went on sale in 1972.
