28 Major Modes
Emacs provides many alternative major modes, each of which
customizes Emacs for editing text of a particular sort. The major modes
are mutually exclusive, and each buffer has one major mode at any time.
The mode line normally shows the name of the current major mode, in
parentheses (see Mode Line).
The least specialized major mode is called Fundamental mode.
This mode has no mode-specific redefinitions or variable settings, so
that each Emacs command behaves in its most general manner, and each
user option variable is in its default state. For editing text of a
specific type that Emacs knows about, such as Lisp code or English
text, you should switch to the appropriate major mode, such as Lisp
mode or Text mode.
Selecting a major mode changes the meanings of a few keys to become
more specifically adapted to the language being edited. The ones that
are changed frequently are <TAB>, <DEL>, and C-j. The
prefix key C-c normally contains mode-specific commands. In
addition, the commands which handle comments use the mode to determine
how comments are to be delimited. Many major modes redefine the
syntactical properties of characters appearing in the buffer.
The major modes fall into three major groups. The first group
contains modes for normal text, either plain or with mark-up. It
includes Text mode, HTML mode, SGML mode, TeX mode and Outline
mode. The second group contains modes for specific programming
languages. These include Lisp mode (which has several variants), C
mode, Fortran mode, and others. The remaining major modes are not
intended for use on users' files; they are used in buffers created for
specific purposes by Emacs, such as Dired mode for buffers made by
Dired (see Dired), Mail mode for buffers made by C-x m
(see Sending Mail), and Shell mode for buffers used for
communicating with an inferior shell process (see Interactive Shell).
Most programming-language major modes specify that only blank lines
separate paragraphs. This is to make the paragraph commands useful.
(See Paragraphs.) They also cause Auto Fill mode to use the
definition of <TAB> to indent the new lines it creates. This is
because most lines in a program are usually indented