Lets recall the prototype of the preprocessor function, which has to be implemented in each preprocessor:
int DLL_EXPORT preproc(pPrepext pEXT,
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.