Else (The C Preprocessor)

#### 4.2.4 Else ¶

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
    text-if-true
    #else /* Not expression */
    text-if-false
    #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.