BCA 4th Semester
Operating System Board Question Paper 2021

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Tribhuvan university

Bachelor In Computer Application

Course Title: Operating System

Code No: CACS 251

Semester:IV

2021

Full Marks:60 Pass Marks:24 Time:3 hours

Candidates are required to answer the question in their own words as far as possible.

Group A
Group B
Attempt any SIX question.
[6x5=30]
2.

What is an Operating System? Why is it known as the resource manager and the extended machine?

3.

What is Kernel? What role does it play in an Operating System? Differentiate between monolithic and micro kernel.

4.

Suppose that a disk has 200 cylinders (0-200). The head pointer is currently at 50 and previously at 35. The queue of pending request, in FIFO order is: 60, 190, 40, 125, 15, and 150. The time required to move per cylinder is 6 msec. Starting from the current head position, what is the total seek time needed to satisfy all the pending request for each of the following disk scheduling algorithms?
a) FCFS
  b) SCAN

5.

Define file and directory. Explain the concept of Access Control List (ACL) and Access Control Matrix (ACM).

6.

What is biometric password in authentication? Explain the various system threats.

7.

How distributed operating system is more applicable than centralized operating system? Explain the major goals of distributed operating system.

8.

Write short notes on any TWO :
a) Producer Consumer problem
b) Coalescing and Compaction
c) Ubuntu

Group C

Attempt any TWO questions

[2x10=20]
9.

What is CPU scheduling? Write down the criteria for CPU scheduling? Consider the following set of processes, with the length of the CPU burst given in milliseconds, draw Gantt chart illustrating their execution and calculate average waiting time and turnaround time using:
a) First Come First Serve
b) Shortest Job First
c) Non-preemptive priority (smaller number implies higher priority)
d) Round Robin (quantum = 1)

ProcessBurst Time (sec)Priority
P0103
P111
P225
P314
P452
The processes have arrived in the order P0, P1, P2, P3, P4 all at time 0.

10.

Define the terms page fault and thrashing. Consider the following page reference string: 1, 3, 5, 1, 7, 1, 5, 5, 1, 4, 2, 7, 6, 3, 4, 1. How many page faults would occur for each of the following page replacement algorithms assuming 3 page frames?
a) FIFO page replacement
b) LRU page replacement
c) Optimal page replacement

11.

Define deadlock. List out the conditions that can result in resource deadlock. Explain different deadlock handling methods in detail.