The Open Source Zone

To quote the Emacs Manual:

Emacs is the extensible, customizable, self-documenting real-time display editor. If this seems to be a bit of a mouthful, an easier explanation is Emacs is a text editor and more. At its core is an interpreter for Emacs Lisp (``elisp'', for short), a dialect of the Lisp programming language with extensions to support text editing. Some of the features of GNU Emacs include:

• Content sensitive major modes for a wide variety of file types, from plain text to source code to HTML files.
• Complete online documentation, including a tutorial for new users.
• Highly extensible through the Emacs Lisp language.
• Support for many languages and their scripts, including all the European ``Latin'' scripts, Russian, Greek, Japanese, Chinese, Korean, Thai, Vietnamese, Lao, Ethiopian, and some Indian scripts. (Sorry, Mayan hieroglyphs are not supported.)
• A large number of extensions which add other functionality. The GNU Emacs distribution includes many extensions; many others are available separately--even a web browser