Last update: 4/4/2000
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The Slide Rule was invented by William Oughtred in 1625. The slide rule is based on Napier's ideas about logarithms - it has logarithmic scales that can be slid past each other to allow approximations to multiplication to be carried out quickly and easily.
Slide rules were in continual use by scientists and mathematicians right up until to the introduction of the first handheld calculator by Hewlett Packard in 1972.