Sample Examination

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
MULTIPLE-CHOICE QUESTIONS (MCQ) EXAMINATION
DURATION : 90 MINUTES
General Instructions
Name Matriculation No. Typ
A
SS07
Page 1
• This is a multiple-choice questions exam. Answer on the Multiple-Choice Solution Sheet
provided.
• This is a closed book exam and no reference books and materials are allowed. No
calculators and other electronic devices are allowed.
Annotation to the Assignments and the Multiple-Choice Solution Sheet
• A set of the assignment sheets, a page of the multiple-choice solution sheet and some
working papers will be provided in an envelope to each student. Do not use your own
paper.
• Only the multiple-choice solution sheet will be evaluated. Marked answers on the
assignment sheet, solution approaches and workings will not be evaluated.
• No corrections on the markings on the multiple-choice solution sheet is allowed. In case
of erroneous entries on the solution sheet, ask the examiner for a new multiple-choice
solution sheet and give up the invalid copy.
• For each sub-task of an assignment, one or more answers may be correct.
But : If the box "None of them" of one sub-task is shaded, the other shaded answers
to this sub-task will be disregarded.
• A negative score is not attainable in any sub-task of an assignment.
• Hand in everything (assignment sheets, multiple-choice solution sheet and the working
papers - used and unused) at the end of the examination in the envelope.
• Only examinations that are returned completely with a signature on the declaration page
will be evaluated.
• Fill in your name and matriculation number on the assignment sheets and the multiplechoice
solution sheets.

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
SS07
Page 2
Assignment 1 (20 Points)
An operating system is an important part of almost every computer system. A computer system
can be divided into four components: the hardware, the operating system, the application
programs, and the user. Most modern computers use disks as primary on-line storage medium
for information, both programs and data. The file system provides the mechanism for online
storage of and access to both data and programs residing on the disks.
1.1 Concerning operating systems and file systems, which statements are true?
A:2 An operating system is a program that acts as an intermediary between the user of a
computer and the computer hardware
B: A soft real-time system guarantees that critical tasks be completed on time and are
used for industrial control and robotics
C:2 Time sharing and time-shared operating systems allow many users to use the
computer system interactively at the same time
D: Parallel systems have only one CPU with their individual computer bus and
separated memory and peripheral devices
E:2 A person whose job is to write programs for the level n virtual machine need not be
aware of the underlying interpreters and translators
F:2 Mass storage media is distinctive from main memory. The former retain data even
when the computer is switched off.
G: Directory organisation refers to various techniques for storing large amount of data
H:2 The file system FAT16 is more reliable against bad sectors than FAT12
I: The file system depends on the technology of the hard disk
J: The file system FAT32 uses the lower order 32 bits for cluster addressing
K: None of them

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
SS07
Page 3
CSMA/CD, carrier sense multiple access/collision detection, is a set of rules determining how
network devices respond when two devices attempt to use a data channel simultaneously.
Standard Ethernet networks use CSMA/CD mechanism and enable network devices to detect a
collision.
Token Ring is a type of computer network in which all the computers are arranged
schematically in a circle. When capitalized, Token Ring refers to the PC network architecture
developed by IBM. The IBM Token-Ring specification has been standardized as the IEEE 802.5
standard. Token-passing networks move a small frame, called a token, around the network.
1.2 Concerning CSMA/CD and Token Ring, which statements are true?
L: CSMA/CD uses a token to announce that the common cable is now used
M:2 CSMA/CD demands that a station has to wait a random time in case of collision
before trying a new transmission
N: CSMA/CD is a deterministic media access method
O:2 CSMA/CD is a statistical media access method
P:2 The CSMA/CD protocol is designed to provide fair access to the shared channel so
that all the stations get a chance to use the network
Q: In a Token Ring several stations can send a message simultaneously
R:2 In a Token Ring network, the active monitor removes continuously circulating frames
from the ring when its sending device fails
S: If no station in a Token Ring wants to send data, the token is kept by the active
monitor
T: Token Ring is a deterministic media access method
U:2 Ethernet networks are use in applications where delays must be predictable and
where applications require a robust network operation
V: None of them

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
SS07
Page 4
Assignment 2 (9 Points)
A local area network operates Ethernet with CSMA/CD mechanism and runs at a
transmission rate of 8 Mbps and a one-way signal propagation time of 25 μs.
2.1 What is the minimum transmitted frame length (bits)?
A: 300 B: 500 C: 800
D: 200 E:3 400 F: None of them
2.2 How long (μs) has a station to wait before trying to access the channel again, after
experiencing 5 successively collisions?
G: 125 H: 625 I: 800
J:3 1 600 K: 3 200 L: None of them
Looking at a Token-Ring network with a Token-Holding-Time (THT) of 10ms and a
transmission rate of 10 Mbps.
2.3 What is the longest frame size (bits)?
M: 25 000 N: 12 500 O:3 100 000
P: 200 000 Q: 50 000 R: None of them

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
SS07
Page 5
Assignment 3 (16 Points)
Definition:
• Runtime is the time a process needs to solve a given task, if it would not be interrupted
• The process control block is called pcb
• A quantum is a small unit of continuous CPU time (tQ). After this quantum has elapsed,
the scheduler changes to the next process (respectively to the method)
• A change of the current process (changing the pcb) takes tC = 1ms
• Changing the pcb is not part of a quantum
• The response time tR is the time between the input event for a process and its response
There are 10 different processes running on a workstation. Idle processes are waiting for an
input event in the input queue. Busy processes are scheduled with the Round-Robin timesharing
method.
3.1 Which out of the following quantum times is the best value for small response times, if
the processes have a short runtime, e.g. less than 10ms?
A:4 tQ = 15ms B: tQ = 40ms C: tQ = 45ms D: tQ = 50ms
3.2 Which out of the following quantum times is the best value concerning CPU efficiency, if
the processes have a long runtime, e.g. greater than 1s?
E: tQ = 10ms F: tQ = 50ms G: tQ = 100ms H:4 tQ = 250ms

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
Consider the following set of processes, with the length of the CPU-burst time given in
milliseconds:
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Process Burst Time Priority
P1 10 3
P2 1 1
P3 2 3
P4 1 4
P5 5 2
Assume that P 1 is at the head of the ready queue and P5 is at the tail, and ignore the
time for changing inter-processes.
3.3 Using Round Robin scheduling algorithm (where the quantum q= 1ms) which is the
average turnaround time?
I: tav = 12ms J:8 tav = 9.2ms
K: tav = 7ms L: tav = 10.8ms M: None of these

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
SS07
Page 7
Assignment 4 (20 Points)
With the Dijkstra Algorithm the shortest path from a source node to any other node in the
network can be calculated, if the network topology is known. The method starts with a list S
of all nodes (except the source node) and calculates the arrays D[v] and R[v]. In D[v] the
current distance from source node to the node v is stored. R[v] contains all nodes which lay
on the shortest route from source to node v. The list and the arrays are initialized as follows:
Initialize list S to include all nodes except the source node.
Initialize array D in the way, that D[v] is the weight of the edge/link from the source to v if the
edge/link exists, otherwise with “infinitive”. R[v] is initialized with the source node, if edge/link
from source to v exists, otherwise with Null (empty).
Given is the following network topology. Use Dijkstra’s Algorithm to define the shortest path
from a to each node.
a
10
Figure 4.1: Network topology
4.1 What is the shortest distance from node a to node b ?
A: 5 B: 7 C:5 8
D: 9 E: 10 F: None of these
4.2 What is the shortest distance from node a to node c ?
G: 5 H: 7 I: 8
5
J:5 9 K: 10 L: None of these
b
e
2
3
1
2
9
7
4 6
c
d

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
4.3 What is the shortest distance from node a to node d ?
M: 5 N:5 7 O: 8
P: 9 Q: 10 R: None of these
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4.4 Using the Dijkstra algorithm, how many routes were replaced with routes of shorter
distance? (Neglecting replacement of infinity values)
S: 1 T: 2 U:5 3
V: 4 W: 5 X: None of these

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
SS07
Page 9
Assignment 5 (15 Points)
5.1. Consider a swapping system in which memory consists of the following hole sizes in memory
order:
H0 H1 H2 H3 H4 H5 H6 H7
10K 4KB 20KB 18KB 7KB 9KB 12KB 15KB
and a successive segment request of
a) 12 KB
b) 10KB
c) 9KB
Which of the following sentences is/are true?
A:2 First Fit algorithm allocates H2, H0, H3 for the mentioned request.
B: Next Fit algorithm allocates H3, H6, H7 for the mentioned request.
C: Best Fit algorithm allocates H2, H0, H3 for the mentioned request.
D: First Fit algorithm allocates H2, H6, H7 for the mentioned request.
E: Worst Fit algorithm allocates H2, H3, H6 for the mentioned request.
F:2 Next Fit algorithm allocates H2, H3, H5 for the mentioned request.
G:2 Best Fit algorithm allocates H6, H0, H5 for the mentioned request.
H:2 Worst Fit algorithm allocates H2, H3, H7 for the mentioned request.
I: None of them

University
Duisburg-Essen
Prof. Dr.-Ing. Axel Hunger
Dipl. Ing. Bogdan Marin
SAMPLE EXAMINATION PAPER
Operating Systems and Computer Networks (ISE)
Data Processing 2 (AOS & E-Technik)
5.2. A computer with a 16 bit address, a 4KB page size, has 64K of VA and 32K of PA.
The page table for this computer is given in the following figure.
Assuming that at a given time the running process issues the following instruction:
MOV REG, 12292
Which will be the outcome of the Memory Management Unit mapping?
J:
K:
L:
M:
N:7
Page table
MOV REG, 12292
MOV REG, 5000
MOV REG, 16388
MOV REG, 4
None of them
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
000
000
000
000
111
000
101
000
000
000
011
100
000
110
001
010
0
0
0
0
1
0
1
0
0
0
1
1
1
1
1
1
Present
bit
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