Emacs
GNU Emacs www.gnu.org/software/emacs/ is the most popular and most ported Emacs text editor, and it was created by Richard Stallman for the GNU Project.

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 variety of file types including plain text, source code, and HTML
- 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
- A large number of extensions that add other functionality, including a project planner, mail and news reader, debugger interface, calendar, and more. Many of these extensions are distributed with GNU Emacs; others are available separately.

Emacs is a toolkit for building a productive environment.