In the late 1950s, while on the faculty of Harvard University, Kenneth Iverson devised an extension of mathematical notation for the precise description of algorithms. Then, along with Adin Falkoff and other researchers at IBM, the team gradually turned the notation into a full-fledged programming language called APL. The language uses an extended character set requiring a specialized keyboard and appears on the page as strings of sometimes unfamiliar symbols—but the underlying consistency of the language makes it easy to learn, and its unmatched array-processing capabilities make it extraordinarily powerful. Its spiritual descendents, J and K, continue APL's legacy of concise and powerful algebraic manipulations.