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 8.5 Initializing a Variable with ‘defvar’
 =========================================
 
 The ‘copy-region-as-kill’ function is written in Emacs Lisp.  Two
 functions within it, ‘kill-append’ and ‘kill-new’, copy a region in a
 buffer and save it in a variable called the ‘kill-ring’.  This section
 describes how the ‘kill-ring’ variable is created and initialized using
 the ‘defvar’ special form.
 
    (Again we note that the term ‘kill-ring’ is a misnomer.  The text
 that is clipped out of the buffer can be brought back; it is not a ring
 of corpses, but a ring of resurrectable text.)
 
    In Emacs Lisp, a variable such as the ‘kill-ring’ is created and
 given an initial value by using the ‘defvar’ special form.  The name
 comes from “define variable”.
 
    The ‘defvar’ special form is similar to ‘setq’ in that it sets the
 value of a variable.  It is unlike ‘setq’ in two ways: first, it only
 sets the value of the variable if the variable does not already have a
 value.  If the variable already has a value, ‘defvar’ does not override
 the existing value.  Second, ‘defvar’ has a documentation string.
 
    (There is a related macro, ‘defcustom’, designed for variables that
 people customize.  It has more features than ‘defvar’.  (Setting
 Variables with ‘defcustom’ defcustom.)
 

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· defvar and asterisk
 

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