Format of device block, argument block for BH=15h:
Offset	Size	Description	)
 00h	WORD	logical unit/device number
 02h	WORD	logical unit/device type
 04h	WORD	display model number
 06h	WORD	numeric checking
 08h	WORD	status line
 0Ah	BYTE	unprotected normal field attribute
 0Bh	BYTE	unprotected intensified field attribute
 0Ch	BYTE	protected normal field attribute
 0Dh	BYTE	protected intensified field attribute
 0Eh	WORD	reserved
 10h	WORD	printer port number