INT F1 - Common ISDN 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. (CAPI) v1.1 - "API-MANUFACTURER" - VENDOR-SPECIFIC
	AH = FFh
	other registers vendor-specific
Return: registers vendor-specific
Range:	INT 00 to INT FF, selectable by program parameter
Notes:	the caller is required to provide at least 512 bytes of stack space
SeeAlso: AH=01h,AH=F0h,AH=F1h,AH=F2h,INT F1/AH=FFh