Questions
Syllabus
Qns. By Syllabus

Semester

Subject

Year

Tribhuwan University

Institute of Science and Technology

2080.1

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.
How DMA operation is performed? Consider a disk with 200 tracks and the queue has random requests from different processes in the order: 45, 48, 29, 17, 80, 150, 28 and 188. Find the seek time using FIFO, SSTF and SCAN. Assume the initial position of head as 100.[10]
2.
How do you distinguish between deadlock and starvation? Describe. Explain working mechanism of TLB.[10]
3.
Why do we need to schedule process? Find the average waiting time and average turnaround time for the following set of processes using FCFS, SJF, RR (Quantum = 3) and shortest remaining time next.

$\begin{array}{|c|c|c|} \hline \text{Process} & \text{CPU burst time} & \text{Arrival time} \\ \hline P1 & 20 & 0 \\ P2 & 25 & 15 \\ P3 & 10 & 30 \\ P4 & 15 & 45 \\ \hline \end{array}$
[10]
Section B

Short Answers Questions

Attempt any Eight questions.
[8*5=40]
4.
What is system call? Describe the transition between different states of process. [5]
5.
Discuss about contiguous and linked list file allocation technique. [5]
6.
Why do we need virtual memory? Describe the structure of a page table. [5]
7.
Illustrate the term safe and unsafe state in deadlock prevention with scenario. [5]
8.
How lock variable is used in achieving mutual exclusion? Describe. [5]
9.
Why do we need hierarchical directory system? Explain structure of disk. [5]
10.
Find the number of page fault using FIFO and LRU for the reference string 4, 7, 6, 1, 7, 6, 1, 2, 7, 2 with frame size 3. [5]
11.
Define working set. How does clock replacement algorithm works? [5]
12.
Write short notes on : a. Inode b. RAID [5]