Difference between revisions of "History of Computers - Slide Rule"

Revision as of 17:48, 14 September 2009

This page was created by Geoff Dunn.

The slide rule is an analog mechanical computer invented in 1622. It was used widely for calculations up until the 1970s when the scientific calculator was invented, a much easier and more convenient way to calculate.

Overview

The logarithm, invented by John Napier and later published in 1614, was originally for the purpose of quickly calculation multiplication and division problems using addition and subtraction instead. In 1620, Edmund Gunter, an English mathematician and astronomer, had the idea that it would be helpful to have a rough scale of these logarithms and put the logarithms proportionately on a line, called the logarithm scale. Later, Reverend William Oughtred put two of these lines side by side and use the two scales together by sliding them for multiplication and division. Because he was the first to do so, he is considered the inventor of the slide rule. Oughtred first invented the circular slide rule and then later the straight slide rule; he also introduced the use of "x" as a sign of multiplication and the abbreviations "sin" and "cos" for sine and cosine. In the course of history, the slide rule was changed from Oughtred's design to the modern design of two bars holding a sliding bar in between them. The slide rule was used for the next 300 years as a reliable and choice instrument for calculation.

Significance

The significance of the slide rule lies in many areas of history. Initially, it was used for scientific and mathematical calculations. However, in more modern history, it has been used to calculate artillery trajectories to measurements for engineers. In WWII, aviators used the slide rule to calculate range, fuel use, and altitude of the aircraft. The slide rule, in the 20th century, has been the symbol of engineers. Wernher Von Braun, a German scientist who worked for the United States during the Space Race, did not use any other calculation device aside from the slide rule; many other scientists during the Space Race also relied on the slide rule as well. Man was able to fly into space and reach the moon with calculations done with the slide rule. The slide rule helped man into space, which in turn (during the Space Race) led to many inventions that we now use, such as Global Positioning Satellites (GPS), cordless power tools, freeze-dried food, fiber optics, satellite dish technology, ear thermometers, fire-resistant fabrics, smoke detectors, and many more. As a result of the Space Race, that could arguably be driven by the slide rule because of such an important role it played, furthered the development of computers. The slide rule's role is great and without it, the world would be much less developed and many of our technologies would not have been developed yet because people would not have been able to make such large calculations so quickly without the slide rule.

Links

http://www.sliderule.ca/

http://www.hpmuseum.org/sliderul.htm

Image of circular slide rule: [1]

References

http://en.wikipedia.org/wiki/Slide_rule

http://www.sliderule.ca/

http://en.wikipedia.org/wiki/Edmund_Gunter#Gunter.27s_scale

http://en.wikipedia.org/wiki/William_oughtred

http://www.hpmuseum.org/sliderul.htm