Slide rule
mechanical analog computer / From Wikipedia, the free encyclopedia
The slide rule, or slipstick,[1] is a mechanical analog computer. The slide rule is used mainly for multiplication and division, and also for "scientific" functions such as roots, logarithms and trigonometry, but usually not for addition or subtraction.
There are many different styles of slide rules. They are usually linear or circular. They have a standardised set of markings or scales. These scales are used for mathematical computations. Some slide rules have been made for special use, as for aviation or finance. Those slide rules have special scales for those applications, as well as normal scales.
The slide rule is based on the work on logarithms by John Napier and was invented by William Oughtred. Before electronic calculators were developed, slide rules were the tool used most often in science and engineering. The use of slide rules continued to grow through the 1950s and 1960s even as digital computing devices were gradually introduced; but around 1974 the pocket calculator made the slide rule largely obsolete and most suppliers left the business.