Introduction

You are reading about GNU Emacs, the GNU incarnation of the advanced, self-documenting, customizable, extensible editor Emacs. (The `G' in `GNU' is not silent.)

We call Emacs advanced because it provides much more than simple insertion and deletion. It can control subprocesses, indent programs automatically, show two or more files at once, and edit formatted text. Emacs editing commands operate in terms of characters, words, lines, sentences, paragraphs, and pages, as well as expressions and comments in various programming languages.

Self-documenting means that at any time you can type a special character, Control-h, to find out what your options are. You can also use it to find out what any command does, or to find all the commands that pertain to a topic. See section Help.

Customizable means that you can alter Emacs commands' behavior in simple ways. For example, if you use a programming language in which comments start with `<**' and end with `**>', you can tell the Emacs comment manipulation commands to use those strings (see section Manipulating Comments). Another sort of customization is rearrangement of the command set. For example, you can rebind the basic cursor motion commands (up, down, left and right) to any keys on the keyboard that you find comfortable. See section Customization.

Extensible means that you can go beyond simple customization and write entirely new commands--programs in the Lisp language to be run by Emacs's own Lisp interpreter. Emacs is an "on-line extensible" system, which means that it is divided into many functions that call each other, any of which can be redefined in the middle of an editing session. Almost any part of Emacs can be replaced without making a separate copy of all of Emacs. Most of the editing commands of Emacs are written in Lisp; the few exceptions could have been written in Lisp but use C instead for efficiency. Writing an extension is programming, but non-programmers can use it afterwards. See Emacs Lisp Intro: (eintr)Top section `Preface' in An Introduction to Programming in Emacs Lisp, if you want to learn Emacs Lisp programming.

When running on a graphical display, Emacs provides its own menus and convenient handling of mouse buttons. In addition, Emacs provides many of the benefits of a graphical display even on a text-only terminal. For instance, it can highlight parts of a file, display and edit several files at once, move text between files, and edit files while running shell commands.

This document was generated by Mark Kaminski on July, 3 2008 using texi2html 1.70.