UNIVERSITY EXAMINATIONS: 2019/ 2020
EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE IN
INFORMATION TECHNOLOGY/ BUSINESS INFORMATION
TECHNOLOGY/ APPLIED COMPUTING/ SOFTWARE DEVELOPMENT/
INFORMATION SECURITY & FORENSCIS
BIT 1106A/ BBIT 111/ BAC 1102/ BSD 1104/ BISF 1102: OPERATING
SYSTEMS
FULL TIME/PART TIME/DISTANCE LEARNING
DATE: MAY, 2020 TIME: 6 HOURS
INSTRUCTIONS: Answer ALL Questions
SECTION B: (20 MARKS)
QUESTION ONE
a) Argue the case for or against the favor for I/O bound processes over CPU-bound
processes [4 Marks]
b) Discuss why it is a good idea to write the disk-scheduling algorithm as a separate module
of the operating system [4 Marks]
c) Describe how system calls work [2 Marks]
d) Describe how access control list are used as protection mechanism [4 Marks]
e) There are five processes A to E to run. Their arrival times are 0, 2,4,10, and 12 second
respectively. Their processing times are 3,5,2,5 and 5 seconds respectively.
Required: calculate the average turnaround time using First-Come-First-served
processing scheduling algorithm. [6 Marks]
Note: show your workings
SECTION C: (20 MARKS)
QUESTION ONE
a) Linux and windows boost priority of I/O bound processes. Explain why this is a good
idea and whether this can lead to starvation of CPU bound processes. [5 Marks]
b) Assume that a process is in its critical section guarded by mutex when it creates a fatal
error that causes the process to be killed. Explain how this could affect other processes
and suggest a way the operating system can eliminate the problem [6 Marks]
c) Explain why it is necessary to store recently used data e.g. recently referenced pages in
cache [3 Marks]
d) Describe how deadlock prevention works by denying some of the necessary conditions of
a deadlock [6 Marks]
