### The Slide Rule

The slide rule is a hand-held arithmetical instrument, formerly of great practical importance.
Until the 20th-Century, the slide rule was one of only a handful of machines with the capability of amplifying the power of the human mind.

Simple slide rules provide multiplication and division, typically to 3 or 4 significant decimal places, and possibly squaring and square rooting.
More elaborate slide rules, such as the Post Versalog ( a sweet machine ) and various Keuffel & Esser rules, are capable of a whole suite of "advanced" calculations, using powers, exponents, roots, logarithms, trigonometric functions, and inverses of those functions.

Sometimes, a slide rule was informally referred to as a "slip stick", based on its shape, being much longer than wide, and on the sliding of the scales past one another.
Circular slide rules providing basic functions were never common.
Cylindrical slide rules are capable of greater accuracy, but uncommon.
Many variations on the slide rule were produced for various specialized purposes, often having nothing to do with the arithmetical operations.

Here are some misspellings :
"Sliderule", "slideruler" and "slide ruler".

2010 Mathematics Subject Classification : Primary 00A99
Secondary 26-01, 26A09

```Walter Nissen
2013-03-30
```