User manual

mikroC PRO for PIC32
MikroElektronika
263
Directives #ifdef and #ifndef
The #ifdef and #ifndef directives can be used anywhere #if can be used and they can test whether an identier
is currently dened or not. The line
#ifdef identier
has exactly the same effect as #if 1 if identier is currently dened, and the same effect as #if 0 if identier
is currently undened. The other directive, #ifndef, tests true for the “not-dened” condition, producing the opposite
results.
The syntax thereafter follows that of #if, #elif, #else, and #endif.
An identier dened as NULL is considered to be dened.