ISRO-DEC2017-62

Question

A system uses $FIFO$ policy for page replacement.It has $4$ page frames with no pages loaded,
to begin with.The system first accesses $50$ distinct pages in some order and then accesses
the same $50$ pages in reverse order.How many page faults will occur?

• A. $96$
• B. $100$
• C. $97$
• D. $92$

Comments

50 + 46 = 96

Answer 1

50 distinct pages(forward) - 50 page replacements

reverse order- first 4 pages will be already loaded- then remaining 46 page replacements

total 96

Answer 2

Access to 50 pages will cause 50-page faults. When these pages are accessed in reverse order, the first four accesses will not cause the page fault. All other access to pages will cause page faults. So total number of page faults will be 50 + (50-4) = 50 + 46 = 96.