The Reverend William Oughtred and others developed the slide rule
in the 17th century based on the emerging work on logarithms by
John Napier. Before the advent of the electronic calculator, it
was the most commonly used calculation tool in science and
engineering. The slide rule's ease of use, ready availability,
and low cost caused its use to continue to grow through the 1950s
and 1960s, even as electronic computers were being gradually
introduced. The introduction of the handheld electronic scientific
calculator around 1974 made slide rules largely obsolete, and most
suppliers left the business.
https://en.wikipedia.org/wiki/Slide_rule
William Oughtred (1574–1660), also Owtred, Uhtred, etc., was an
English mathematician and Anglican clergyman. After John Napier
invented logarithms and Edmund Gunter created the logarithmic scales
(lines, or rules) upon which slide rules are based, Oughtred was the
first to use two such scales sliding by one another to perform direct multiplication and division. He is credited with inventing the slide
rule in about 1622. He also introduced the "×" symbol for multiplication
and the abbreviations "sin" and "cos" for the sine and cosine functions.
https://en.wikipedia.org/wiki/William_Oughtred
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