Node: Else, Next: , Previous: Defined, Up: Conditional Syntax


The #else directive can be added to a conditional to provide alternative text to be used if the condition fails. This is what it looks like:

     #if expression
     #else /* Not expression */
     #endif /* Not expression */

If expression is nonzero, the text-if-true is included and the text-if-false is skipped. If expression is zero, the opposite happens.

You can use #else with #ifdef and #ifndef, too.