MAASAI MARA UNIVERSITY
UNIVERSITY EXAMINATIONS 2015/2016 (REGULAR)
SCHOOL OF SCIENCE AND INFORMATION SCIENCES
UNIVERSITY EXAMINATIONS FOR THE DEGREE OF BACHELOR
OF SCIENCE (COMPUTER SCIENCE)
SECOND YEAR SECOND SEMESTER EXAMINATION
COURSE CODE: COM 223
COURSE TITLE: OPERATING SYSTEM AND NETWORKING
DATE: 27TH AUGUST 2015
INSTRUCTIONS
 Answer Question ONE and any other TWO
TIME: 11.00 – 13.00
SECTION – A
QUESTION ONE (COMPULSORY 30 MARKS)
(a) What is an operating system? Explain any four desirable objective of an
operating system?
(5 marks)
(b) Explain what do you understand by virtual machines?
(4 marks)
(c) Define the following terms:
(i)
Process
(ii)
Multiprogramming
(iii)
Real time
(iv)
Time sharing
(4 marks)
(d) A Process play important role during the program execution. Explain all
the five stages of a process.
(5 marks)
(e) Explain the internal structure of operating system where kernel plays
important role in the computer operations.
(2 marks)
(f) ) Explain any FOUR criteria for evaluating scheduling algorithm.
(4 marks)
g) What are the differences between segmentation and paging?
(4 marks)
h) Explain all three different type of computer memory with the help of
memory hierarchy.
(2 marks)
SECTION – B
QUESTION TWO (20 marks)
a)
(i) What do you understand by serial processing?
(2 marks)
(ii) Write any three Limitations of Serial Processing.
(2 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?
(3 marks)
c) What is the difference between Preemptive and. Non-preemptive SJF
scheduling?
(3 marks)
d) Briefly explain the Shortest-Job-First (SJF) and give its main disadvantage.
(3 marks)
e) What is in a thread control block?
(2 marks)
f)
(i) Explain Batch Processing with an example.
(2 marks)
(ii) List any three Drawbacks of batch processing.
(3 marks)
QUESTION THREE (20 marks)
a) Explain all the three access modes for operation on a file.
(6 marks)
b) Briefly explain how the SCAN and CSCAN disk head scheduling algorithms
work. Also give one demerit of each of the algorithms above.
(6 marks)
c) What is spooling? Why is a printer spooling system better than direct user
access to printers?
(4 marks)
d) (i) What is SRT scheduling?
(2 marks)
(ii) Find out the average waiting time using SRT scheduling of the following:
Job
Arrival time
Burst time
1
0
7
2
1
4
3
3
9
4
4
5
(2 marks)
QUESTION FOUR (20 marks)
(a) (i) What do understand by file attributes?
(1 mark)
(ii)Explain any three categories of file attributes?
(3 marks)
b)
(i) What is a deadlock situation.
(2 marks)
(ii) Explain any four necessary conditions for a deadlock to occur.
(4 marks)
c) How can we avoid deadlock situation? Justify your answer.
(4 marks)
d) Consider a disk queue with request of I/O to block on cylinder
98, 183, 37, 122, 14, 124, 65, 67
If the disk head is initially at cylinder 53, then calculate total number of head
movements using following algorithms:
i
FCFS
(3 marks)
ii
SSTF
(3 marks)