Emacs is the premier text editor and programming environment for workstations and high-end PCs. This manual tells you how to get started with Emacs, how to write simple messages as well as complex documents, and how to use special modes for editing, compiling, and debugging programs. It also explains how to handle multiple files and directories and multiple windows, and how to customize your environment. GNU Emacs provides autosave, multiple undos and redos, transparent access to remote file systems, multiple backups, support for version control systems, and a Lisp interpreter. In addition, Emacs integrates make, grep, diff, and other utilities into a single environment. There are modes for programming in over a dozen different languages. Emacs not only works with plain character terminals but also is fully integrated with the X Window System. Emacs includes an on-line, easy to follow tutorial and a built-in help system that describes all of Emacs's features. This is the 13th edition of the GNU Emacs Manual. It is written by Richard M. Stallman, who wrote the original Emacs. This edition describes the new features and improvements in version 20. All funds raised from the sale of this book are used to support the development of free software and free documentation.