Format of HOPEN parameter block:
Offset	Size	Description	)
 00h	WORD	0003h (length of following data)
 01h	BYTE	initialization flags
		bit 6: don't load default palette
		bit 7: clear bitplanes
 02h	BYTE	mode type (see #03910)
 03h	BYTE	(ret) return code
		bit 7: no adapter (hardware mismatch)
SeeAlso: #03898