Operating Systems 2080

Section A
Long Answer Questions
Attempt any TWO questions. [2 × 10 = 20]

1. Why is Optimal Page Replacement the best but not practically feasible page replacement algorithm? Calculate the number of page faults for Optimal, LRU, and FIFO replacement algorithms for the reference string: 1, 3, 4, 2, 3, 5, 4, 3, 1, 2, 4, 6, 3, 2, 1, 4, 2 using 3 page frames. [1+9]

2. Find the average waiting time and turn-around time for the following example using FIFO, SRTF, and Round Robin scheduling algorithms. Assume quantum as 4 ms.

3. Why is virtual memory technique used in the computer system? What is a logical address? Explain the process of conversion of logical address to physical address using TLB. [5+5]

Section B
Short Answer Questions
Attempt any EIGHT questions. [8 × 5 = 40]

4. Suppose that a disk drive has cylinders numbered 0 to 199 and is currently serving a request at cylinder 143. The request queue is kept in FIFO order: 25, 17, 119, 197, 194, 15, 182, 115, 183. What is the total head movement needed to satisfy these requests for the following disk scheduling algorithms:
(a) FCFS
(b) SSTF [5]

5. A 2 GB disk has a 4-KB block size. Calculate the size of the file allocation table if each entry of the table is 4 bytes. [5]

6. What is a process? Explain the 3-state process model with a suitable diagram. [1+4]

7. Write down the basic difference between coalescing and compaction with a diagram. [5]

8. What is memory-mapped I/O? Explain device-independent I/O software. [1+4]

9. Differentiate between deadlock and starvation. Discuss the process of detecting deadlocks when there are multiple resources of each type. [1.5+3.5]

10. Differentiate between a process and a program. What is a PCB? [3+2]

11. Write down the solving technique of the producer-consumer problem with message passing. [5]

12. What is a system call? Explain the system call process in detail. [1.5+3.5]