?? ????? ?? ??? ?? ???? ??? ??? ? ??? ???? ???? ????? ?? ??? ? ??? ???? ??? ?? ????? ?????????? ???? ???????? ???? ???? ?????? ???? ????? ??? ?? ???? ???? ?? ????? ???? ???? ???? ??‌???. The idea of dirty bits has existed for many years. The very first recognized usage of dirty bits was with