Emacs ( /ˈiːmæks/) is a family of text editors, characterized by their extensibility. One manual describes it as "the extensible, customizable, self-documenting, real-time display editor." Development began in the mid-1970s and continues actively as of 2012. Emacs has over 2,000 built-in commands and allows the user to combine these commands into macros to automate work, in particular with the use of Emacs Lisp, a variant of Lisp, providing a deep extension capability.
The original EMACS consisted of a set of Editor MACroS for the TECO editor. It was written in 1976 by Richard Stallman, initially together with Guy L. Steele, Jr. It was inspired by the ideas of TECMAC and TMACS, a pair of TECO-macro editors written by Steele, Dave Moon, Richard Greenblatt, Charles Frankston, and others.
In Unix culture, Emacs became one of the two main contenders in the traditional editor wars, the other being vi. The word "emacs" is often pluralized as emacsen, by analogy with boxen (itself used by analogy with oxen) and VAXen.
The most popular (and most ported) version of Emacs is GNU Emacs, created by Stallman for the GNU Project. Another version in common use, XEmacs, was forked from GNU Emacs in 1991. XEmacs has remained mostly compatible and continues to use Emacs Lisp like GNU Emacs.