INT 21 U - Sun PC-NFS - 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.???
	AX = 44E0h
	DS:DX -> ???
	SS:BP -> stack frame (see #01589)
Return: ???
Note:	this function is also supported by Beame&Whiteside's BWPCNFS shim; the
	  description presented here was derived from that shim


Format of PC-NFS stack frame:
Offset	Size	Description	(Table 01589)
 00h	WORD	-> previous stack frame
 02h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	return address