Emacs is a class of feature-rich text editors, usually characterized by their extensibility. Development began in the mid-70s and, as of 2008, is still active. Emacs text editors are most popular with technically proficient computer users and computer programmers. The most popular version of Emacs is GNU Emacs, a part of the GNU project, which is commonly referred to simply as "Emacs".

The GNU Emacs manual describes it as "the extensible, customizable, self-documenting, real-time display editor." It is also the most ported of the implementations of Emacs. As of September 2008, the latest stable release of GNU Emacs is version 22.3.

Aside from GNU Emacs, another version of Emacs in use is XEmacs, which is a fork of GNU Emacs started in 1991. XEmacs has remained mostly compatible and continues to use the same extension language, Emacs Lisp, as GNU Emacs. Almost all of GNU Emacs and XEmacs are written in Emacs Lisp, so the extensibility of Emacs' features is deep.

The original EMACS was 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 is 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.

History

Emacs development began at the MIT AI Lab during the 1970s. Before its introduction, the default editor on the Incompatible Timesharing System (ITS), the operating system on the AI Lab's PDP-6 and PDP-10 computers, was a line editor known as Text Editor and Corrector (TECO). Unlike most modern text editors, TECO has separate modes which the user used to either add text, edit existing text, or display the document. Typing characters into TECO did not place those characters directly into a document; one had to write a series of instructions in the TECO command language telling it to enter the required characters, during which time the edited text was not displayed on the screen. This behavior is similar to the program ed.

Richard Stallman visited the Stanford AI Lab in 1972 or 1974 and saw the lab's "E" editor, written by Fred Wright.Fact: date=June 2007 The editor had an intuitive WYSIWYG behavior as is used almost universally by modern text editors, which impressed Stallman. He returned to MIT where Carl Mikkelsen, a hacker at the AI Lab, had added a combined display+editing mode called "Control-R" to TECO, allowing the screen display to be updated each time the user entered a keystroke. Stallman reimplemented this mode to run efficiently, then added a macro feature to the TECO display-editing mode, allowing the user to redefine any keystroke to run a TECO program.Fact: date=June 2007