ALCCS
Code: CS31
Subject: OPERATING
SYSTEMS
NOTE:
· Question 1 is compulsory and
carries 28 marks. Answer any FOUR questions from the rest. Marks are indicated against each question.
· Parts of a question should be
answered at the same place.
Q.1
a. Differentiate between multiprogramming,
multitasking, timesharing and multiprocessing systems.
b. Briefly explain Process Control Block (PCB).
c. What is a semaphore? What is its use?
d. What is a system call? How it is different from a Library Call?
e. Differentiate between physical address and logical address.
f. What is the meaning of the term busy waiting? What other
kinds of waiting are there? Can busy waiting be avoided
altogether?
g. What is the difference
between logical clock and physical clock? Briefly explain with an
example. (74)
Q.2 a. Explain how short term,
medium term, and long term scheduler work giving suitable example. (9)
b.
Explain Synchronous and Asynchronous RPC (Remote Procedure Call) mechanism with
an example. (9)
Q.3 a. What are the benefits of a
distributed file system when compared with a file in a
centralized
system? (9)
b.
What aspects of a distributed system would you select for a system running
on a totally reliable network?
(9)
Q.4 a. Write Banker’s safety algorithm and prove
that the Banker’s safety algorithm requires an order of M N2 operations. (9)
b. What do you mean
by critical section? Using semaphores, write a solution to the readers and writers problem that gives
priority to readers.
(The readers and writers problem: any number of readers may
simultaneously be reading from a file, and no reader can be reading while a
writer is writing). (9)
Q.5 a. Consider the following snapshot of a
system:
Allocation Max Available
ABCD ABCD ABCD
P0 0012 0012 1520
P1 1000 1750
P2 1354 2356
P3 0632 0652
P4 0014 0656
Answer the following questions
using Banker’s algorithm:
i) What is the content of matrix Need?
ii) Is the system in a safe state?
iii) If a request from P1 arrives
for (0,4,2,0), can the request be granted immediately? Apply banker’s safety
algorithm to test this. (9)
b. How many types of multiprocessor Operating
Systems are there? Explain its functions and requirements. (9)
Q.6 a. When do page faults
occur? Describe the actions taken by the operating system when a page
fault occurs.
(6)
b. What is the cause of thrashing? How
does the system detect thrashing? What are the models
used to avoid thrashing. (6)
c. Explain
Direct Memory Access? How does DMA increase system concurrency? How does it complicate hardware design? (6)
Q.7 Write
the short notes on:
(a) Interrupt Handlers
(b) Election
Algorithms in Distributed OS.
(c) Starvation & Aging (6+6+6)