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Comp 206: Operations Systems Question Paper
Comp 206: Operations Systems
Course:Bachelor Of Science In Computer Science
Institution: Chuka University question papers
Exam Year:2013
CHUKA
UNIVERSITY
UNIVERSITY EXAMINATIONS
SECOND YEAR EXAMINATIONS FOR THE AWARD OF DEGREE OF BACHELOR OF SCIENCE IN COMPUTER SCIENCE
COMP 206: OPERATIONS SYSTEMS
STREAMS: B.SC (COMP SCIENCE) Y2S1 TIME: 2 HOURS
DAY/DATE: MONDAY 22/4/2013 8.30 AM – 10.30 AM
INSTRUCTIONS:
Answer question ONE in Section A and any other TWO questions in Section B
Marks are awarded for clear and concise answers.
SECTION A
Question One Compulsory – (30 Marks)
(a) (i) Using relevant example(s) define the term operating system. [3 Marks]
(ii) Explain four functions in file, process and memory management performed by
windows operating system. [4 Marks]
(iii) Distinguish between multi-user and multiprocessing operating systems.
[4 Marks]
(b) Give three reasons why an operating system should require memory management.
[3 Marks]
(c) Highlight any two levels of directory organization [2 Marks]
(d) What is demand paging and what are its advantages. [3 Marks]
(e) Context switching in operating system is the switching of the CPU from one process to
another.
(i) What are the three scenarios where context switches need to occur. [3 Marks]
(ii) Describe the steps for a context switch. [4 Marks]
(f) Differentiate between pre-emptive and non-preemptive scheduling as used in CPU scheduling. [4 Marks]
SECTION B: (40 Marks) choose two Questions
Question two (20 Marks)
(a) Explain the following terms as they are used in the scheduling criterion:
(i) CPU utilization
(ii) Turnaround time
(iii) Waiting time
(iv) Response time [8 Marks]
(b) Explain four services provided by an operating system. [8 Marks]
(c) Explain two major complications that concurrent processing adds to an operating system. [4 Marks]
Question three (20 Marks)
(a) Using the round robin scheduling algorithm, answer the question that follow. Consider for example, the following scenario of four jobs and the corresponding CPU burst time and the arrival time
Process Arrival Time Burst Time
P1 0 7
P2 2 4
P3 4 1
P4 5 4
Using shortest job next algorithm
(i) Show the resultant Gantt chart [4 Marks]
(ii) Calculate the waiting time of the jobs. [3 Marks]
(iii) What will be the total turnaround time of the jobs? [3 Marks]
(b) Describe the process control block and the various pieces of information that it contains
in regard to process management. [10 Marks]
Question four (20 Marks)
(a) (i) Given memory partitions of 100k, 500k,200k,300k and 600k (in order), place the
following processes; 212k, 417, 112, and 462k (in order) using
(i) First-fit
(ii) Best-fit
(iii) Worst-fit [6 Marks]
(ii) From (a) above advice on the algorithm that uses the memory effectively.
[1 Mark]
(iii) Explain the term thrashing and state its disadvantages. [3 Marks]
(b) Explain three algorithms used by memory manager to allocate a new created or swapped in process. [6 Marks]
(c) Explain the following terms:
(i) Fetch policy
(ii) Replacement policy [4 Marks]
Question five (20 Marks)
(a) Give three schemes that can be employed to prevent deadlock from occurring. For each
scheme, illustrate a disadvantage of using it. [6 Marks]
(b) Describe briefly main memory management based on the following:
(i) Paging [2 Marks]
(ii) Relocation and swapping [2 Marks]
(c) Describe the difference between external and internal fragmentation. [6 Marks]
(d) Describe the strategy behind deadlock prevention and give an example of a practical deadlock prevention method. [4 Marks]
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