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(elisp)Global Variables

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Global Variables
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   The simplest way to use a variable is "globally".  This means that
the variable has just one value at a time, and this value is in effect
(at least for the moment) throughout the Lisp system.  The value remains
in effect until you specify a new one.  When a new value replaces the
old one, no trace of the old value remains in the variable.

   You specify a value for a symbol with `setq'.  For example,

     (setq x '(a b))

gives the variable `x' the value `(a b)'.  Note that `setq' does not
evaluate its first argument, the name of the variable, but it does
evaluate the second argument, the new value.

   Once the variable has a value, you can refer to it by using the
symbol by itself as an expression.  Thus,

     x => (a b)

assuming the `setq' form shown above has already been executed.

   If you do set the same variable again, the new value replaces the old
one:

     x
          => (a b)
     (setq x 4)
          => 4
     x
          => 4