635: Mainline

You use both an #ifdef–#endif combination and an #ifndef–#endif combination if you want to compile some lines if a definition exists and others if it does not. Alternatively, you can use a single #ifdef–#else–#endif combination:

#ifdef VERBOSE 
...             | 
...             | <-- Compile if VERBOSE has been defined 
...             | 
#else 
...             | 
...             | <-- Compile if VERBOSE has NOT been defined 
...             | 
#endif