@comment  node-name,  next,  previous,  up
@node Modes, Files, Help, Top
@chapter Major and Minor Modes
@cindex modes

XEmacs is @dfn{language sensitive}. It has several @dfn{major} and
@dfn{minor} modes.  The major modes customize Emacs to edit text of a
particular sort. There are major modes for C, Lisp, Emacs Lisp, LaTeX,
English etc. Within each major mode, certain functions and keys are
redefined to "suit" that particular sort of text. The minor modes
provide certain features which can be turned off or on at any
time. Emacs can only be in one major mode at any time, but it can turn
on several minor modes at the same time. After you have selected any
major or minor mode, you can select @b{Describe Mode} from the @b{Help}
menu and you will get documentation about those modes. 

@comment  node-name,  next,  previous,  up
@menu
* Major Modes::                 Choosing Major Modes
* Minor Modes::                 Auto-Fill, Abbrev and other minor modes
@end menu

@node Major Modes, Minor Modes, Modes, Modes
@section Major Modes
@cindex major modes

Emacs has several major modes which customize Emacs to edit text of
various sorts. You can have only one major mode at any time. Within each
major mode, Emacs redefines certain functions (like cursor movement,
indentation and text killing) to suit the needs of the text being
edited. When you are editing a specific type of text you should switch
to the appropriate mode. If you are working with C code, you should
switch to C mode; if you are working with Lisp code, then switch to lisp
mode and if you are working with English text switch to Text mode.

        When you open a file to work on, Emacs usually selects the
appropriate mode. For example, if you open a file called @file{guide.c}
then Emacs will select the C mode because of the ".c" extension of the
file. To explicitly select a mode type the following command:

@example
;;; selects lisp mode
M-x lisp-mode

;;; selects C mode
M-x c-mode
@end example

@noindent
To select any other mode, just add the major mode name before the
'-mode'. The current mode in which you are in will be displayed in
parenthesis in the mode-line at the bottom of the frame. All major
modes have some special keybindings and you can get a listing of those
keybindings by selecting @b{List Keybindings} from the @b{Help} menu on
the menu bar.

        Some of the available modes in XEmacs are :

@table @b
@item fundamental-mode 
@cindex fundamental-mode
When you start XEmacs, usually you start with the default "Fundamental"
mode. This mode has no special definitions or settings.   

@item nroff-mode
@cindex nroff-mode
Use this mode when you have to format a text with nroff before it can be
available in readable form. It redefines some indentation
commands. @xref{Nroff Mode,,,xemacs,XEmacs User's Manual}, for information
on this mode.

@item tex-mode
@cindex tex-mode
Use this mode if you are using the LaTeX text-formatter. It provides
commands for insertion of quotes, braces and other characters. It also
allows you to format the buffer for printing. @xref{TeX
Mode,,,xemacs,XEmacs User's Manual}, for information on this mode.

@item texinfo-mode
@cindex texinfo-mode
Texinfo is a documentation system that uses a single source file to
produce both printed output and on-line documentation. When you use this
mode, there will be some special keybindings for inserting some
characters and executing some commands.

@ifinfo
This info file which you are reading right now is produced by 'Texinfo'
@end ifinfo
@iftex
This manual itself is produced by 'Texinfo'
@end iftex

@item outline-mode
@cindex outline-mode
Use this mode for editing outlines. When you enable this mode, you can
make part of the text temporarily invisible so that you can see the
overall structure of the outline. @xref{Outline Mode,,,xemacs,XEmacs User's
Manual}, for information on this mode.

@item c-mode
@cindex c-mode
Use this mode for C programs. It will redefine some indentation
commands. @xref{C Indent,,,xemacs,XEmacs User's Manual}.

@item lisp-mode
@cindex lisp-mode
Use this mode for Lisp programs. Look at the XEmacs User's Manual for
more information.

@item fortran-mode
@cindex fortran-mode
Use this mode for Fortran programs. This mode provides special commands
to move around and some other indentation commands.  For more
information on this mode, @xref{Fortran,,,xemacs,XEmacs User's Manual}.

@item edit-picture
@cindex edit-picture
This is the picture mode which you can use to create a picture out of
text characters. @xref{Picture,,,xemacs,XEmacs User's Manual}, for more
information.

@item asm-mode
@cindex asm-mode
Use asm-mode for editing files of assembler code. Look at the file 
@file{ /usr/local/lib/xemacs-VERSION/lisp/modes/asm.el} for more
information. 

@end table

There are some other modes and commands for working with other kinds of
text or programs. Emacs also provides commands for reading and sending
Mail. For more information on these features look at the XEmacs
Manual. Emacs also provides the functions of a desk calendar, with a
diary of past or planned events. For more information on the calendar
mode look at the manual for Calendar Mode and Diary.

@comment  node-name,  next,  previous,  up
@node Minor Modes,  , Major Modes, Modes
@section Minor Modes
@cindex minor modes

The minor modes in Emacs provide some optional features which you can
turn on or off. Any number of minor modes can be active at the same time
with any major mode. You can enable a minor mode in one buffer and
disable it in other mode. To enable a minor mode, for example the
font-lock mode type the following command: 

@example
M-x font-lock-mode
@end example
@noindent
To enable the other minor modes, replace the "font-lock" with the
name of the minor mode. To disable the mode type the command again. A
positive argument will always turn the mode on. Whenever you type this
command, it will turn the mode on if it was off, OR it will turn it off
if it was on i.e. it toggles. Look at the mode-line at the bottom of the
frame. If it says FLock in parentheses, then it means that this
mode is on, otherwise it is off. 

The following are some of the minor modes available in XEmacs. To enable
any one of them type "M-x" in front of them.

@table @b
@item font-lock-mode
@cindex font-lock-mode

You can also choose this mode by selecting the @b{Syntax Highlighting}
menu item from the @b{Options} menu on the menu-bar at the
top. If you wish to have this mode enabled permanently, choose 
@b{Save Options} from the @b{Options} menu. @xref{Options Menu}, for
more information on the Options menu.  You can also add statements in
your @file{init.el} file. For each major mode in which you wish to
enable this minor mode, you need a statement in your @file{init.el}
file. The following example shows how to enable the font-lock mode when
the major mode is c-mode. 

@example
(add-hook 'c-mode-hook          'turn-on-font-lock)
@end example

@noindent
@xref{Other Customizations}.

When you enable this mode, the text will be displayed in
different colors and fonts depending on the type of the text. This makes
the text very easy to read and understand. For example, comments might
be displayed in red, variables in black, functions in blue and other
keywords in different colors and fonts. When you select @b{More} from
the @b{Syntax Highlighting} option, you get very detailed display of
colors and fonts; function names within comments themselves might appear
in a different font and color.  

@item auto-fill-mode
@findex auto-fill-mode
Enabling this mode will provide automatic word-wrapping. The @key{SPC}
key will break lines i.e. insert newlines as you type to prevent lines
from becoming too long. 

@item overwrite-mode
@cindex overwrite-mode
When you enable this mode, the text that you type will replace the
existing text rather than moving it to the right (the default case). You
can enable this mode by selecting @b{Overstrike} menu-item from the
@b{Options} menu from the menu-bar. 

@item abbrev-mode
@cindex abbrev-mode
After you enable this mode, you can define words which will expand into
some different text i.e. you can define abbreviations. For example, you
might define "expand" to "expand will eventually expand to this
text". After this definition you will be able to get "expand will
eventually expand to this text" simply by typing 

@example
expand @key{SPC} 
@end example

@noindent
 @xref{Abbrevs,,,xemacs,XEmacs User's Manual}, for more information on this
mode and on defining abbreviations.

@item auto-save-mode
@cindex auto-save-mode
After you enable this mode in a buffer, the contents of that buffer will
be saved periodically. This will reduce the amount you might lose in
case of a system crash.

@item line-number-mode
@cindex line-number-mode
After you enable this mode, the line number at which your cursor is
present will be displayed continuously in the mode line. 

@item blink-paren
@cindex blink-paren
To enable this command, just type 
@example
M-x blink-paren
@end example

@noindent
Do not add the "-mode" to it.  You can also select the @b{Paren
Highlighting} option from the @b{Options} menu. After you enable this
command, put your cursor on one of the left parenthesis. The other
matching parenthesis will start blinking. @xref{Options Menu}, for more
information on the @b{Paren Highlighting} option.
@end table

For information on some other modes, look at the XEmacs User's Manual
and the associated files.

