INT 21,31 - Terminate Process and Remain Resident

	AH = 31h
	AL = exit code (returned to batch files)
	DX = memory size in paragraphs to reserve

	returns nothing

	- preferred method for Terminate and Stay Resident programs
	- terminates process without releasing allocated memory and
	  without closing open files
	- attempts allocation of memory specified in DX from memory
	  allocated by DOS at startup.	 INT 21,48 memory allocation
	  is not affected

	- see	INT 27