#define MAIN_CARD 0x00 #define AUXILIARY_CARD 0xFF #define AUXILIARY_CARD_1 0x01 #define AUXILIARY_CARD_2 0x02 #define AUXILIARY_CARD_3 0x03 #define AUXILIARY_CARD_4 0x04 #define AUXILIARY_CARD_5 0x05 #define AUXILIARY_CARD_6 0x06 #define AUXILIARY_CARD_7 0x07 #define AUXILIARY_CARD_8 0x08
The meaning of these specific values (0, 0xFF,1..8) is application-specific, as is the significance of the identifiers (like NAME_CARD). If you're looking for information on how the #define directive works, see the K & R book or any C or C++ reference book.