Slide rule
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.