On-line version

http://www.gnupress.org/software/emacs/elisp-manual/

Emacs Lisp is much more than an "extension language" for the GNU Emacs program. It is a full programming language in its own right. Because Emacs Lisp was designed to be used by an editor, it has developed unique features for scanning and parsing text, as well as for handling files, buffers, displays, subprocesses and more. Emacs Lisp is also closely integrated with the Emacs editing facilities. As a result, editing commands are functions that can be conveniently be called from Lisp programs, and act as parameters for customization of regular Lisp variables.

This reference manual is the only manual that specifically covers Emacs Lisp. The earlier chapters describe the features similar to those in many programming languages. The later chapters describe features specific to Emacs Lisp or that are specifically related to editing. It also includes an introductory section for programmers who are new to Lisp.

This edition is completely revised to cover Emacs Version 21, with an appendix noting differences for Emacs Version 20.