qc.hlp (Table of Contents; Topic list)
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defined
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  Operator:  defined
 
  Syntax:    defined ( identifier )
             !defined ( identifier )
 
  Summary:   Used with the #if directive to test whether <identifier>
             is currently defined. Returns true (nonzero) if it is
             currently defined, or false (0) if it is not. The logical
             NOT operator (!) can be used to reverse the logic of the
             defined operator. For example,
 
                  #if defined( OS2 )
                  #if defined( OS2 ) && !defined( PM )
 
  See also:  #define, #if, #ifdef, #ifndef, #undef
                                    -♦-