Emacs is the extensible, customizable, self-documenting real-time display editor. 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.)