Calculator

A.D. 1671 : Leibniz's Calculator
The first calculator that could perform automatic addition,subtraction as well as multiplication and division was developed by a German philosopher Gottfried Wilhem Von Leibniz.

Leibniz Calculator Fig. A2.5

It worked on the principle that multiplication and division can be accomplished by repetitive addition and subtraction respectively.
In 1694,Leibniz modified his calculator.It was also known as Stepped Reckoner.
It consisted of a drum upon which teeth were mounted,nine at one end.A gear wheel was positioned on the shaft mounted along the drum.The gear wheel could be moved to mesh in with the teeth of the drum at any position.
For example to multiply by 5 the gear wheel was moved 5 positions on the drum. One revolution of the drum moved the gear wheel through 5 teeth, two revolution through 10 and so on. The carry-over mechanism was also employed. Leibniz used the new concept of binary system in a calculating machine.