OS WEEKLY TEST QUESTIONS (12-3-18)

DESCRIPTIVE QUESTIONS

1. A) Define page fault. When does a page fault occur?
    B) Describe the action taken by OS when page fault occurs with diagram.

2. A)Consider the following page reference string

        7,0,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0   Assuming three frames, how
     many page faults would occur in each of the following cases:

         i) LRU                ii) FIFO

    B) State and Explain Belady’s anomaly with an example.


Fill in the blanks

1. Virtual memory is
(a) Large secondary memory (b) Large main memory
(c) Illusion of large main memory (d) None of the above

2 . Optimal page – replacement algorithm is difficult to implement, because :
a) it requires a lot of information b) it requires future knowledge of the reference string
c) it is too complex d) it is extremely expensive

3. The two methods how LRU page replacement policy can be implemented in hardware are COUNTER,REFERENCE BIT.

4. LRU stands for__________________________________________.

5. OPTIMAL PAGE REPLACEMENT yields the lowest of all possible page-faults,