The #undef Statement
Sometimes you need to cause a defined name to become undefined. You do this with the #undef statement. To remove the definition of a particular name, you write the following:
#undef name
Therefore, this statement removes the definition of IPAD:
#undef IPAD
Subsequent #ifdef IPAD or #if defined (IPAD) statements evaluate to FALSE.
This concludes our discussion on the preprocessor.
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