Emacs ("the extensible, customizable, self-documenting real-time display editor", according to its manual) is based around a Lisp interpreter (itself written in C), with the bulk of the functionality then written in Lisp. Because of this design, it is easy for programmers and users to add functionality to Emacs. Many have done so, and Emacs can be used to surf the web, read email and [Usenet news]?, play tetris and provide basic AI psychoanalysis. In addition, Emacs can serve as an IDE (integrated development environment), allowing programmers to edit, compile, and debug their code within a single interface.
Two popular version of Emacs are [GNU Emacs]? and XEmacs.
Emacs is an example of a buffer gap editor, in which the contents of a document are stored in a data structure which consists of a single buffer with a gap where the current edit point resides. As a result, editing operations such as adding or deleting a few characters do not have to modify much memory, and operations such as searching are relatively simple. The competing form of storage for documents is to store each line of the document in a small buffer. Unfortunately, Emacs efficiency at manipulating text is often outweighed by the inefficiency of its interpreted Lisp code, leading to the joke that EMACS stands for Eight Megabytes And Constantly Swapping. Fortunately, modern computers have plenty of memory and performance to run Emacs.
The current version of GNU Emacs is 21.1, released on October 20th, 2001.
It is part of the culture of many programmers to treat their favorite editor with a religious reverence bordering on fanaticism, and to make fun of themselves doing so. There is an active Usenet group alt.religion.emacs devoted to the Emacs side of the "holy war" with its major competitor, vi. Users have also created myths, dogma, rituals, and other trappings of religion in honor of the editor.
See also:
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