INT D4 - PC-MOS/386 v5.01 - CHANGE TERMINAL DRIVER                              
	AH = 23h
	BX = task ID (FFFFh for current task)
	DS:SI -> entry point of the new Device DriverAn interface module between the device-independent portions of the operating system and an actual hardware device which converts device-independent requests into the actual sequence of device operations to perform the requested action.  IO.SYS contains the standard, built-in MSDOS device drivers such as CON, COM1, AUX, PRN, etc.  See also INT 21h Function 52h and INT 2Fh Function 0802h. Terminal
Return: CF clear if successful
	CF set on error
	    AX = error code (see #01680 at INT 21/AH=59h/BX=0000h)