Format of REAL/32 Memory Physical Parameter Block:
Offset	Size	Description	)
 00h	WORD	4K page number in first megabyte to be mapped
 02h	WORD	number of page to map into above page, or 0000h to unmap
 04h	WORD	window number (0000h, as only one window currently supported)
 06h	WORD	reserved
Note:	all users of the system share the window, so applications should not
	  use it for arguments to system calls, attempt to read/write to/from
	  files via the window, etc.