INT 21 - XPACK v1.52+ - SET TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user.  The name comes from the name of the DOS function call used to remain in memory after termination. STATUS
	AX = 37A3h
	BX = 6A6Dh ('jm')
	DL = status (01h active, 00h disabled)
Return: AX = 0000h (successful)
SeeAlso: AX=37A0h/BX=6A6Dh,AX=37A2h/BX=6A6Dh