Lets recall the prototype of the preprocessor function, which has to be implemented in each preprocessor:
int DLL_EXPORT preproc(pPrepext pEXT,
long *pCmd,
void *p);
This function has to be implemented in each internal preprocessor and is called when the preprocessor is loaded or when some the processing of the source program has reached a certain point. To inform the function about this point the argument pCmd is used. This argument points to a long that holds the a constant identifying the reason why the preprocessor function was called. The following subsections list these identifiers.