Name of the Program: B.Sc. in SWE Semester:
Winter 2020-2021
Date: 8 September 2021 Time: 2:30 pm - 4:00 pm
ISLAMIC UNIVERSITY OF TECHNOLOGY (IUT) ORGANISATION OF
ISLAMIC COOPERATION (OIC) Department
of Computer Science and
Engineering (CSE)
SEMESTER FINAL EXAMINATION
COURSE CODE: CSE 4501 (SWE)
COURSE TITLE: OPERATING SYSTEMS
WINTER SEMESTER, 2020-2021
FULL MARKS: 75
DURATION: 1 Hour 30 Minutes
CSE 4501 (SWE): Operating Systems
Programmable calculators are not allowed. Do not write anything on the question paper. There are
total 3 (THREE) questions each with one or more sub-questions. Answer ALL of them. The symbols have
their usual meanings.
Figures in the right margin indicate marks and corresponding CO and PO.
Write Student ID, Name and other details on top of the first page and write student ID and page no in every
page of the answer script. Submission pdf of the answer script should be named as
Full_Student_ID_CSE4501_Final.pdf
1. a) Write a thread program where there will be a 'control thread' that will pass one of the two commands:
START and STOP to the 'processing thread'. The processing thread starts a new 'worker thread' when
START command is received and signals the 'worker thread' to stop when STOP command is received.
(Use POSIX thread library to implement the program. You can write the pseudo code as well. In that case
pseudo code must contain POSIX thread library in it.)
b) Implement the program asked in 1.a) using process and shared memory. (Use POSIX
thread library to implement the program. You can write the pseudo code as well. In that case pseudo
code must contain POSIX thread library in it.)
c) Google's Chrome browser opens each new tab in a separate process. Would the same benefits
have been achieved if Chrome opens each new tab in a separate thread? Explain your answer.
2. a) Although the Shortest Job First (SJF) algorithm is the best of all CPU scheduling algorithms
yet it is not possible to implement practically. Explain why it is not possible to implement it practically.
Explain the approximated implementable SJF algorithm with example.
10
CO4
PO2
10
CO4
PO2
5
CO2
P01
10
CO5
PO2
b) Suppose, the operating system maintains two different ready queues for the Interactive
and Batch processes. Interactive ready queue schedules in RR manner whereas the batch queue
follows FCFS policy. To balance between the queues, 80% of the time is given to the RR queue and
20% of the time is given to the FCFS queue. Draw the Gantt chart and calculate average waiting time
for each of the queue for the given set of processes. Assume quantum time, q=2 unit.
10
CO5
PO1
Process
Burst Time
Arrival Time
Type (Interactive/Batch
Pl
5
0
I
P2
16
3
P3
1
3
P4
8
P5
17
5
7
B
I
I
B
3.
c)
A well-known company has hired you for designing a system running I/O-bound processes and
CPU-bound processes. While considering different processes, you find out there is a mix of long
and short processes. For better and secured performance, you have differentiated the
processes to execute in the kernel-level while the rest will execute at the user-level.
Now, as an OS developer, your task is to select a scheduling algorithm that will give better performance
for the system. Explain your choice.
a) Given memory partition of 200KB, 600KB, 200KB, 400KB and 700KB (in order), how would
each of the first fit, best fit, and worst fit algorithms place for the processes of 215KB, 420KB,
115KB and 430KB (in order)? Which algorithm makes the most efficient use of memory?
5
CO5
PO2
10
CO2
PO2
b) Consider a paging system with TLB and hit ratio of 80%. If the memory access time is 150
nanoseconds and the searching time for TLB is 50 nanoseconds what is the effective memory
access time for the following cases?
10
CO2
PO2
i. When the page-table entry is found in the TLB?
ii. When the page-table entry is not found in the TLB?
many pages
are possible to be addressed in this paging scheme? If hierarchical paging is adopted
c) In 32-bit addressing scheme, normally a page is constituted of 4kbytes. So, how
with 10-bits for the inner page table, what will be the architecture of the memory management
scheme? Draw a diagram to depict the above hierarchical paging scheme.
5
CO2
PO2