Emacs is a free, portable, extensible text editor available for Linux and UNIX-based systems.
Emacs is an extensible, customizable, self-documenting, real-time display editor. Emacs runs on several operating systems like GNU, GNU/Linux, FreeBSD, NetBSD, OpenBSD, OS X, MS Windows and Solaris. Emacs and its derivatives are a family of text editors that are characterized by their extensibility. Emacs Lisp gives an extension capability allowing users and developers to write new commands using a dialect of the Lisp programming language with different "modes", enabling it to be used like an Integrated Development Environment (IDE) for programming languages like Java, C or Python. Extensions have been written to manage email, files, outlines, and RSS feeds. Emacs provides typed commands and special key combinations that let user to add, delete, insert, and otherwise manipulate words, letters, lines, and other units of text.