UGC NET CSE | September 2013 | Part 3 | Question: 71

Question

Consider a main memory with three page frames for the following page reference string:

5, 4, 3, 2, 1, 4, 3, 5, 4, 3, 4, 1, 4

Assuming that the execution of process is initialized after loading page 5 in memory,, the number of page faults in FIFO and second chance replacement respectively are

• A. 8 and 9
• B. 10 and 11
• C. 7 and 9
• D. 9 and 8

Answer 1

5, 4, 3, 2, 1, 4, 3, 5, 4, 3, 4, 1, 4  page frame are 3                     and  page 5 is already there so no page fault for 5

now execution starts 4 and 3 will come in with page fault no 1 and 2  

acc to FIFO page 2 ,1  will replace 5 and 4 and cause page fault no 3 and 4 and so on

9 w.r.to FIFO is only in choice D so it will be the ans 

Comments

Can u please also explain second chance replacement algorithm. I am getting 9 in both cases

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in second chance if a page is referenced again while the page is present in memory then it is given a second chance(by increasing it reference bit to1 from 0) to stay in memory when its replacement turn comes 

P.S   start counting after 5 

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Please explain it