INT 13 - PCIBM PC Tools v8+ VSAFE, VWATCH - 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 = FAh
	DX = 5945h
	AL = function (00h-07h)
Return: varies by function
	if not installed:
	    CF set
		AH = 01h
Note:	this 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. is identical to the ones on INT 16/AH=FAh and INT 21/AH=FAh,
	  so it is listed in its entirety under INT 16/AX=FA00h and following
SeeAlso: INT 16/AX=FA00h