Bitfields for DPMI page attribute word:
Bit(s)	Description	)
 0-2	page type
	000 uncommitted
	001 committed
	010 mapped (see AX=0508h,AX=0509h)
	other currently unused
 3	page is read/write rather than read-only
 4	accessed/dirty bits supplied in bits 5 and 6
 5	page has been accessed (only valid if bit 4 set)
 6	page has been written (only valid if bit 4 set)
 7-15	reserved (0)