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Bbit 213:Computer Operating System End Of 3Rd Trimester 2016 Question Paper

Bbit 213:Computer Operating System End Of 3Rd Trimester 2016

Course:Bachelor Of Business Information Technology

Institution: Kenya Methodist University question papers

Exam Year:2016

KENYA METHODIST UNIVERSITY

END OF 3RD TRIMESTER 2016 (FT) EXAMINATION

SCHOOL : SCIENCE AND TECHNOLOGY
DEPARTMENT : COMPUTING AND INFORMATION SCIENCE
UNIT CODE : CISY 300/BBIT 213/DBIT 210/DCIS 201
UNIT TITLE : COMPUTER OPERATING SYSTEMS I
TIME : 2 HOURS

INSTRUCTIONS
Answer Question One and any other Two questions
Section A-Compulsory
Question One (30 marks)
a) What are the three main purposes of an operating system? (3 mks)
b) Briefly explain ONE major activity of an operating system with regard to the following:
i. Process Management. (2 mks)
ii. Memory Management. (2 mks)
c) Why is the separation of mechanism and policy desirable in OS design and implementation? (4 mks)
d) Describe the differences among short-term, medium-term, and long-term scheduling. (6 mks)
e) What resources are used when a thread is created? How do they differ from those used when a process is created? (3 mks)
f) Consider the following set of processes, assumed to have arrived at a time 0 in the order as shown below:
Process Burst Time (ms) Priority
P1 10 3
P2 1 1
P3 2 4
P4 1 5
P5 5 2

Using priority scheduling:
i. Schedule the above processes in a Gantt Chart (3mks)
ii. Calculate the average waiting time (3 mks)
g) “A deadlock situation can arise if four conditions hold simultaneously in a system”. Give a concise explanation on the meaning of that sentence. (4 mks)
Question Two (15 marks)
a) Consider the following program:
#include
#include
int main()
{
/* fork a child process */
fork ();
/* fork another child process*/
fork();
/* and fork another */
fork();
return 0;
}
i. Including the initial parent process, how many processes are created in the above program? (1 mk)
ii. Justify your answer in (i). (1 mk)
b) State ONE benefit and ONE disadvantages of each of the following. Consider both the system level and the programmer level.
i. Synchronous and asynchronous buffering (2 mks)
ii. Automatic and explicit buffering (2 mks)
iii. Send by copy and send by reference (2 mks)
c) Using a well-illustrated diagram describe the various states of a process (7 mks)

Question 3 (15 marks)
a) Explain the difference between internal and external fragmentation. (2 mks)
b) Given five memory partitions of 100 KB, 500 KB, 200 KB, 300 KB, and 600 KB (in order):
i. How would the first-fit, best-fit, and worst-fit algorithms place processes of 212 KB, 417 KB, 112 KB, and 426 KB (in order)? (6 mks)
ii. Which algorithm makes the most efficient use of memory? (1mk)
c) In comparing different memory-management strategies, we use specific considerations. Highlight any three considerations. (6 mks)

Question 4 (15 marks)
a) Suppose that the following processes arrive for execution at the times indicated. Each process will run for the amount of time listed. In answering the questions, use non-preemptive scheduling and base all decisions on the information you have at the time the decision must be made.
Process Arrival Time Burst Time
P1 0.0 8
P2 0.4 4
P3 1.0 1

i. What is the average turnaround time for these processes with the FCFS scheduling algorithm? (3 mks)
ii. What is the average turnaround time for these processes with the SJF scheduling algorithm? (3 mks)
b) Is it possible to have a deadlock involving only a single process? Explain your answer. (3 mks)
c) Interpret the tradeoff between fairness and throughput of operations in the readers–writers problem. (3mks)
d) Devise a method for solving the readers–writers problem without causing starvation. (3 mks)

Bbit 213:Computer Operating System End Of 3Rd Trimester 2016 Question Paper

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