GNU Emacs is an extensible, customizable text editor. A large part of the Emacs code base is written in a dialect of Lisp called Emacs Lisp, and the editor can be customized and extended in this language.
Emacs provides context-sensitive editing modes with syntax coloring, is self documenting, has full Unicode support and extensions to do most anything. Die-hard Emacs users do most everything from within Emacs: write code, compile, run, debug, read/compose email, browse the web, do project planning, etc.
- A paper by RMS describing the design of Emacs
- The Emacs Wiki, a collaborative wiki for extensions to Emacs
- Wikipedia's Emacs page
- A tour of Emacs
- Emacs FAQ
- History of Emacs and GPL
- GNU Emacs Manual, 16th Edition, v. 22
- An Introduction to Programming in Emacs Lisp, 3rd Edition