Name

#undef

Synopsis

The #undef directive cancels a macro definition. This is necessary when the definition of a macro needs to be changed, or when a function of the same name needs to be called.

Syntax:

 #undef name

No parameter list needs to be specified, even if the previously defined macro has parameters.

Example:

#include <ctype.h>
#undef  toupper
   . . . 
c = toupper(c);  // Call the function toupper()

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