Questions
Syllabus
Qns. By Syllabus

Semester

Subject

Year

Tribhuwan University

Institute of Science and Technology

2080

Bachelor Level / Second Year / Fourth Semester / Science

B.Sc in Computer Science and Information Technology (CSC264)

(Operating Systems)

Full Marks: 60

Pass Marks: 24

Time: 3 Hours

Candidates are required to give their answers in their own words as for as practicable.

The figures in the margin indicate full marks.

Section A

Long Answers Questions

Attempt any TWO questions.
[2*10=20]
1.
When does the request switch from user mode to kernel mode? Give answer with an example. Find the average waiting time and turnaround time for the process scheduling algorithms FCFS, Priority and RR (Quantum=2) in the following given dataset.
ProcessArrival TimeBurst TimePriorityP0051 (Lowest)P1134 (Highest)P2282P3363\begin{array}{|c|c|c|c|c|} \hline \text{Process} & \text{Arrival Time} & \text{Burst Time} & \text{Priority} \\ \hline P0 & 0 & 5 & 1 \text{ (Lowest)} \\ P1 & 1 & 3 & 4 \text{ (Highest)} \\ P2 & 2 & 8 & 2 \\ P3 & 3 & 6 & 3 \\ \hline \end{array}
[10]
2.
How do you recognize critical section? Why do we need to synchronise it? Consider the request for the page references 7,0,1,2,0,3,0,4,2,3,0,3,2. Find the number of page fault for FIFO and LRU with 4 page frames. [10]
3.
Can deadlock occur in case of preemptive resources? List the conditions for deadlock. Define allocation graph with example. [10]
Section B

Short Answers Questions

Attempt any Eight questions.
[8*5=40]
4.
Explain different memory allocation strategies. [5]
5.
Suppose a disk has 201 cylinders, numbered from 0 to 200. At same time the disk arm is at cylinder 10, and there is a queue of disk access requests for cylinders 30, 85, 90, 100, 105, 110, 135, and 145. Find the total seek time for the disk scheduling algorithm FCFS and SSTF. Assume the head is moving inward. [5]
6.
What are the advantages of using interrupt? Describe. [5]
7.
Differentiate between contiguous and linked list file allocation technique. [5]
8.
Differentiate between paging and segmentation. [5]
9.
What does Belady's anomaly mean? What are the benefits of multiprogramming over uniprogramming? [5]
10.
How can we achieve mutual exclusion? Describe. [5]
11.
What makes thread different with process? Draw the transition diagram between states of a process. [5]
12.
When does a page fault occur? Give a structure of a page table. [5]