Format of REAL/32 Device Map Parameter Block (DEVPB):
Offset	Size	Description	)
 00h	WORD	direction (00h = get current mapping, 01h = set new mapping)
 02h  4 BYTEs	physical device IDs which map into LPT1 - LPT4
 06h  4 BYTEs	physical device IDs which map into COM1 - COM4
Note:	LPT4 and COM3/COM4 are reserved on early versions of Multiuser DOS,
	  but are supported from at least CCI Multiuser DOS v7.22 onward