(lemacs.info)Variables


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Variables
=========

   A "variable" is a Lisp symbol which has a value.  Variable names can
contain any characters, but by convention they are words separated by
hyphens.  A variable can also have a documentation string, which
describes what kind of value it should have and how the value will be
used.

   Lisp allows any variable to have any kind of value, but most
variables that Emacs uses require a value of a certain type.  Often the
value has to be a string or a number.  Sometimes we say that a certain
feature is turned on if a variable is "non-`nil'," meaning that if the
variable's value is `nil', the feature is off, but the feature is on
for any other value.  The conventional value to turn on the
feature--since you have to pick one particular value when you set the
variable--is `t'.

   Emacs uses many Lisp variables for internal recordkeeping, as any
Lisp program must, but the most interesting variables for you are the
ones that exist for the sake of customization.  Emacs does not
(usually) change the values of these variables; instead, you set the
values, and thereby alter and control the behavior of certain Emacs
commands.  These variables are called "options".  Most options are
documented in this manual and appear in the Variable Index (*note
Variable Index::.).

   One example of a variable which is an option is `fill-column', which
specifies the position of the right margin (as a number of characters
from the left margin) to be used by the fill commands (*note
Filling::.).

* Examining
Examining or setting one variable's value.
* Edit Options
Examining or editing list of all variables' values.
* Locals
Per-buffer values of variables.
* File Variables
How files can specify variable values.

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