Language Reference Guide : Preprocessing Your 4GL Code : Preprocessor : The #ifndef - #endif Statement
 
Share this page          
The #ifndef - #endif Statement
The #ifndef statement can be used to test whether a name has not been defined as a macro variable by #define. The syntax for this statement is:
#ifndef $variable
...
#else
...
#endif
The #ifndef statement is TRUE if the macro variable has not been defined.