INT 11 - RainbowFAX v1.3 - SFENGINE 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 = 79h
	AL = subfunction
	    01h set ??? flag
		Return: AX = previous state (0000h already set, 0001h clear)
	    02h clear ??? flag (refer to subfunc 01h)
		Return: AX = 0001h
	    03h set ??? flag (different from subfn 02h or 04h)
		Return: AX = 0001h
	    04h clear ??? flag (different from subfn 02h or 03h)
		Return: AX = 0001h
	    else
		Return: AX = FFFFh (invalid subfunction)
SeeAlso: AH=77h,AH=78h,AH=7Ah,AH=7Ch