INT 13 - XDF.COM - API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running. Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. AH = 18h CX = D2C9h ("R"+80h, "I"+80h = Roger Ivey) DX = 0000h BX = function 0000h installation check Return: AH = 0Ch CX = 7269h ("ri" = Roger Ivey) ES = segment of driver CF set 2F64h ("/d") disable the driver Return: AH = 0Ch ES:BX = pointer to activation flag (it is set to 0: set it to 1 to enable the driver again) CX = 7269h CF set 2F75h ("/u") unload the driver (restore interrupts & free memory) Return: AH = 0Ch DL = 55h ("U") if successful = 00h if fails CX = 7269h ES = segment of driver CF set AL, BX, DH, and DI destroyed Program: XDF is a TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user. The name comes from the name of the DOS function call used to remain in memory after termination. provided with PC-DOS 7.0 to support XDF 1.84M disks, developed by Roger D. Ivey Note: After disabling or enabling the driver, a disk change must be performed or simulated to reset the driver.