Info Catalog elisp: Variables elisp: Constant Variables

elisp: Global Variables

 
 11.1 Global Variables
 =====================
 
 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’ is a special
 form (Special Forms); it 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 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
 

Info Catalog elisp: Variables elisp: Constant Variables