DISPLAY_STRING = 09h
OPEN_FILE = 3Dh
CLOSE_FILE = 3Eh
READ_FILE = 3Fh
ALLOCATE_MEMORY = 48h
FREE_MEMORY = 49h
MODIFY_MEMORY = 4Ah

OPEN_ACCESS_READONLY  = 0000H
OPEN_ACCESS_WRITEONLY = 0001H
OPEN_ACCESS_READWRITE = 0002H