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Bmit 227:Operating System August 2009 Question Paper
Bmit 227:Operating System August 2009
Course:Bachelor Of Business Management And Information Technology
Institution: Kabarak University question papers
Exam Year:2009
KABARAK UNIVERSITY
EXAMINATIONS
2008/2009 ACADEMIC YEAR
FOR THE DEGREE OF BACHELOR OF BUSINESS
MANAGEMENT
& INFORMATION TECHNOLOGY
COURSE CODE: BMIT 227
INSTRUCTIONS:
Note: - Part-A is compulsory, has 40 marks and from Part-B, You can attempt ANY TWO
questions. Each question has 30 marks.
Part-A
Question 1 (40 marks)
a) What is an operating system? How is it related to computer hardware? (3 Marks)
b) Explain any four desirable features of an operating system? (6 Marks)
c) What is the different between virtual machines and real machines? (4 Marks)
d) Definitions for the following terms:
(i) Process
(ii) Multiprogramming
(iii) Non-determinism
(iv) Time sharing (4 Marks)
e) What is the difference between true and concurrency? (4 Marks)
f) Explain all the five stages of a process. (5 Marks)
g) What is the distinction between user mode and kernel mode and why is this distinction
necessary? (4 Marks)
h) (I) What are the differences between segmentation and paging? (6 Marks)
(II) Explain an advantage and disadvantage? (4 Marks)
Question Two (30 marks)
a) What are the four main steps in executing a program instruction? (4 Marks)
b) Consider performance of FCFS algorithm for three compute-bound processes. What if have
3 processes P1 (takes 24 seconds), P2 (takes 3 seconds), and P3 (takes 3 seconds). Their arrival
order is P2, P3, P1, What is the
I. Total Waiting Time?
II. Turnaround Time?
III. Throughput? (6 Marks)
c) What is the difference between Preemptive and. Non-preemptive SJF scheduling? (4 Marks)
d) Briefly explain the Shortest-Job-First (SJF) and give its one disadvantage. (5 Marks)
e) What is in a thread control block? (2 Marks)Page 3 of 4
f) What are the two major ways in which an operating system improves upon a bare machine?
(4 Marks)
g) What is meant by kernel or supervision mode within an operating system?
(2 Marks)
h) Explain any three ways of indicating the type of file (3 Marks)
Question 3 (30 marks)
a) How can you minimize the time spent at high interrupt levels? (2 Marks)
b) Explain Why memory management algorithms are important. (4 Marks)
c) Explain any five issues of CPU scheduling. (10 Marks)
d) (i) Some CPUs cannot support paged virtual memory. Suggest a reason why this might
be so.
(2 Marks)
(ii) Do you know of a CPU that suffers from this problem? (2 Marks)
e) How external fragmentation can be avoided. Explain with an example. (3 Marks)
f) Explain an advantage and disadvantage of two level directory structures. (4 Marks)
g) A variable partition memory system has at some point in time the following hole sizes
in the given order:
20k 15k 40k 60k 10k 25k
A new process is to be loaded of size 25k. Which hole size would be filled using best –fit,
first-fit and worst-fit respectively? (3 Marks)
Question Four (30 marks)
a) Explain any three access modes for operation on a file. (6 Marks)
b) (i) What do understand by file attributes? (2 Marks)
(ii)Explain any three categories of file attributes? (6 Marks)
c) Briefly explain how the SCAN, CSCAN and VSCAN disk head scheduling algorithms
work. Also give one demerit of each of the algorithms above. (6 Marks)
d) What is spooling? Why is a printer spooling system better than direct user access to
printers? (4 Marks)Page 4 of 4
e) Memory compaction is very expensive. This can be made worse by inefficient memory
compaction algorithms. Consider the following memory map:
1) 200K used
2) 300K unused
3) 100K used
4) 200K used
5) 100K unused
6) 300K used
Discuss the various alternatives for compacting this memory, specifically the overhead
required for the compaction. Would it change anything if the sizes of some of the regions were
to vary slightly from multiples of 100K? (6 Marks)
Question Five (30 marks)
a) (i) What is MMU? Explain its work in computer system? (4 Marks)
(ii) Where does MMU exist in computer system? (2 Marks)
(iii) What is virtual and physical memory? (4 Marks)
b) How to prevent priority inversions? (2 Marks)
c) (i) What is a deadlock situation. (2 Marks)
(ii) Explain any four necessary conditions for a deadlock to occur. (8 Marks)
d) How can we avoid a deadlock situation? Justify your answer. (4 Marks)
e) Suppose our system has 12 tape drives. System currently running P0 needs max 10 has 5,
P1 needs max 4 has 2, P2 needs max 9 has 2. Justify your answers for:
I. Can system prevent deadlock even if all processes request the max?
II. If P2 requests two more tape drives, can system give it the drives? (2 Marks)
f) Specify the permission codes which would give read access to all users, write access tom
the owner and his/her group and executable access only to the owner. (2 Marks)
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