GNU Emacs is an extensible, customizable text editor - and more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing.

The features of GNU Emacs include:

• Content-sensitive editing modes, including syntax coloring, for a wide-range of file types
• Complete built-in documentation, including a tutorial for new users
• Full Unicode support for nearly all human languages and their scripts
• Highly customizable, using Emacs Lisp code or a graphical interface
• Includes a project planner, mail and news reader, debugger interface, calendar, and more