INT 21 - DOS 2+ - IOCTL - READ FROM CHARACTER DEVICE CONTROL CHANNEL            
	AX = 4402h
	BX = file handle referencing character device
	CX = number of bytes to read
	DS:DX -> buffer
Return: CF clear if successful
	    AX = number of bytes actually read
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
Notes:	format of data is driver-specific
	  (also see separate entries below for some specific cases)
	this function was not supported by Digital Research's DOS Plus
SeeAlso: AX=4400h,AX=4403h"DOS",AX=4404h"DOS",INT 2F/AX=122Bh
                                                                                

INT 21 U - MS-DOS 7.0+ - CONFIG$ device - GET CONFIGURATION INFORMATION         
	AX = 4402h
	BX = file handle for character device "CONFIG$"
	CX = number of bytes to read (at least 5)
	DS:DX -> buffer for ??? data (see #01444)
Return: CF clear if successful
	    AX = number of bytes actually read
	CF set on error
	    AX = error code (01h,05h,06h,0Dh) (see #01680 at AH=59h/BX=0000h)
SeeAlso: AX=4403h"CONFIG$"


Format of MS-DOS 7.0 CONFIG$ ??? data:
Offset	Size	Description	(Table 01444)
 00h	WORD	??? (0000h)
 02h	WORD	??? (0000h or value read from IO.SYS segment 70h)
 04h	BYTE	??? (value read from IO.SYS segment 70h)