Domain Host Configuration Protocol

Distributed Host Configuration Protocol

Janata Bank Ltd. Assistant Network Engineer (SO) Exam: 2020 | প্রশ্ন ও সমাধান

Question 1Programming

Which is the correct output?

int i = 4;
printf ("%d%d", ++i, i++);
printf ("%d ", i++);

a)5 4 6
b)5 7 8
c)6 4 6
d)4 5 7

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Question 2Programming

Which is not a feature of Java OOP?

a)Multiple Inheritance (correct answer)
b)Multi-level inheritance
c)Compile time Polymorphism
d)Runtime Polymorphism

Answer and explanation

Correct answer: (a) Multiple Inheritance

A Java class can extends only one class, so class C extends A, B is a compile error. Oracle explains that this avoids the problems of multiple inheritance of state, i.e. inheriting fields from several classes. Java does allow a class to implement many interfaces (multiple inheritance of type), and since Java 8 default methods give a limited form of multiple inheritance of implementation. Multiple inheritance of classes, as in C++, is still not a Java feature.

Why the other options are wrong

(b) Multi-level inheritance: Supported. A chain such as class B extends A and class C extends B is legal, because each class still has just one direct superclass.
(c) Compile time Polymorphism: Supported through overloading (same name, different parameter lists). The JLS states that the overload is resolved at compile time.
(d) Runtime Polymorphism: Supported through overriding. A superclass reference calls the subclass's version of the method, chosen at run time (dynamic dispatch).

Tip: Java: one superclass, many interfaces.

Source: Multiple Inheritance of State, Implementation, and Type - The Java Tutorials (Oracle); Chapter 8. Classes, §8.8.8 Constructor Overloading - Java Language Specification (Java SE 8)

Question 3Database

If you are assigned to remove partial dependency from a database, which technique will you use?

a)1NF
b)2NF
c)3NF
d)BCNF

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Question 4Algorithms

Suppose you have a complete undirected graph with 4 nodes. What is the maximum number of minimum spanning trees (MSTs) you can form?

a)4
b)8
c)16
d)1

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Question 5Networking

Which one of the following is the default port of HTTP?

a)23
b)25
c)80
d)45

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Question 6Data Structures

What will be the state of a queue after executing the following operations?

push(1), push(2), pop(), push(4), push(5), pop()

a)2, 5
b)2, 4
c)4, 5
d)1, 4

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Question 7Computer Architecture

Which one is the wrong statement for the BIOS of a computer?

a)Connects microprocessor and I/O
b)Manages data flow
c)Loads the operating system
d)Provides storage (correct answer)

Answer and explanation

Correct answer: (d) Provide storage

The question asks for the statement that is NOT true of the BIOS. The BIOS (Basic Input/Output System) is firmware on the motherboard that runs before the operating system. It tests the hardware with the Power-On Self Test (POST), offers basic input/output routines through which software talks to devices, and then loads the boot loader, which starts the operating system. Apart from holding its own code and settings in a ROM/flash chip, it offers no storage space for programs or user data; that is the job of RAM and secondary storage.

Why the other options are wrong

(a) Connect microprocessor and I/O: A true statement. The BIOS initialises the I/O devices, and its I/O routines link the processor and software with the hardware.
(b) Manages data flow: A true statement. Through the same routines it handles data flow between the operating system and attached devices such as the keyboard, disk and display.
(c) Loads the operating system: A true statement. After POST it finds a boot device and loads the boot loader, which brings up the OS.

Tip: BIOS = POST + basic I/O services + loading the OS. Storing data is never a BIOS function.

Sources: How to Update BIOS – Intel; Introducing UEFI-Compliant Firmware on IBM System x and BladeCenter Servers (IBM); Win32_BIOS class (Microsoft Learn)

Question 8Networking

DHCP means?

a)Dynamic Host Control Protocol
b)Domain Host Configuration Protocol
c)Distributed Host Configuration Protocol
d)Dynamic Host Configuration Protocol (correct answer)

Answer and explanation

Correct answer: (d) Dynamic Host Configuration Protocol

DHCP is the Dynamic Host Configuration Protocol, defined in RFC 2131. A DHCP server leases an IP address to each client and also supplies other settings such as the subnet mask, default gateway (router) and DNS servers, so hosts need no manual setup. A client gets its lease through the four-message DORA exchange: Discover → Offer → Request → Acknowledge. DHCP runs over UDP: clients send to server port 67 and servers reply to client port 68.

Why the other options are wrong

(a) Dynamic Host Control Protocol: The "C" stands for Configuration. DHCP hands hosts their configuration; it does not control them.
(b) Domain Host Configuration Protocol: "Domain" belongs to DNS, the Domain Name System. The "D" in DHCP is Dynamic, because addresses are leased from a pool and returned when no longer used.
(c) Distributed Host Configuration Protocol: Not the name of any protocol. DHCP is a client/server protocol in which a server hands out the settings.

Tip: DHCP = Dynamic + Host + Configuration: it configures hosts automatically.

Source: RFC 2131: Dynamic Host Configuration Protocol

Question 9Database

Which one is not a database transaction property?

a)Atomicity
b)Consistency
c)Durability
d)Quality (correct answer)

Answer and explanation

Correct answer: (d) Quality

Database transactions are defined by the four ACID properties:

Atomicity: all of a transaction's operations take effect, or none do.
Consistency: each committed transaction leaves the data obeying every integrity constraint.
Isolation: a transaction's changes stay invisible to other transactions until it commits.
Durability: committed changes survive crashes and power failures.

"Quality" is a general word, not one of the four, so it is the odd one out.

Why the other options are wrong

(a) Atomicity: The A in ACID.
(b) Consistency: The C in ACID.
(c) Durability: The D in ACID. (Isolation, the I, is simply not listed.)

Tip: Transaction properties = ACID. If an option is not Atomicity, Consistency, Isolation or Durability, it is the answer.

Source: PostgreSQL Documentation: Glossary

Question 10Networking

How many bits in IPv6?

a)32
b)64
c)128
d)156

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Question 11Cyber Security

How can we prevent SQL Injection Attack?

a)Show the database error to the users
b)Do not remove potential malicious code
c)Use the user input directly
d)Use input validation (correct answer)

Answer and explanation

Correct answer: (d) Use input validation

SQL injection happens when user input is treated as part of an SQL command. Validating input, ideally against an allow-list of expected values, formats and lengths, stops malicious SQL fragments before they reach the query. OWASP lists allow-list input validation among its primary defences and also as a secondary layer. The strongest primary defence is prepared statements (parameterised queries), which keep data and code separate; least-privilege database accounts limit the damage if something slips through. Input validation is the only protective practice among these options.

Why the other options are wrong

(a) Show the database error to the users: raw database error messages reveal table names, column names and query structure, which helps an attacker refine the injection; errors should be logged privately and users shown a generic message.
(b) Do not remove potential malicious code: leaving suspicious input untouched means injected SQL reaches the query; this is the opposite of a defence.
(c) Use the user input directly: concatenating raw user input into an SQL string is the root cause of SQL injection; OWASP's vulnerable example simply appends an unvalidated parameter to the query.

Exam note: OWASP's first-choice fix is prepared statements with parameterised queries; input validation is listed as a primary defence (option 3) and as an extra layer. It is correct here because it is the only defensive choice offered.

Tip: Never build SQL by joining strings with user input: parameterise first, validate always.

Source: SQL Injection Prevention - OWASP Cheat Sheet Series

Question 12Networking

A complex bandpass signal has a bandwidth of 300 kHz. What is the minimum sampling rate for this signal?

a)600,000 samples per second
b)600,00 samples per second
c)600 kHz
d)None of the above

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Question 13Networking

The human voice normally contains frequencies from 0 to 4000 Hz. If we sample at the Nyquist rate using 8 bits per sample, what is the required bit rate?

a)8000 samples/second
b)8000 kbps
c)64 kbps
d)64 samples/second

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Question 14Networking

Which one is the loopback address?

a)255.255.255.0
b)127.0.0.1
c)255.0.0.0
d)127.127.127.0

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Question 15Networking

Which one is not the purpose of modulation in a communication system?

a)To reduce antenna size
b)To save energy to transmit information
c)To transmit signals from various sources
d)To make the system simpler and cost effective

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Question 16Networking

Five channels, each with a 100-kHz bandwidth, are to be multiplexed together. What is the minimum bandwidth of the link if there is a need for a guard band of 5 kHz between the channels to prevent interference?

a)500 kHz
b)520 kHz
c)540 kHz
d)525 kHz

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Question 17Networking

Assume we need to download text documents at the rate of 100 pages per sec. Each page contains an average of 24 lines with 80 characters in each line. If we assume that one character requires 8 bit, what is the required bit rate of the channel?

a)1.92 Mbps
b)1.636 Mbps
c)1.82 Mbps
d)1.536 Mbps

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Question 18Networking

Consider an extremely noisy channel in which the value of the signal-to-noise ratio is almost zero. For this channel, if the bandwidth is B then what is the channel capacity?

a)0.137B
b)0
c)0.137
d)Infinity

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Question 19Digital Logic

A binary counter is being pulsed by a 256 kHz clock signal. The output frequency from the last flip-flop is 2 kHz. Which one of the following is the counting range?

a)0 to 255
b)0 to 128
c)0 to 127
d)None of the above

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Question 20Web Technology

When a web browser interacts with a web server, the following actions take place.

A1: The web browser requests a webpage using HTTP.
A2: The web browser establishes a TCP connection with the web server.
A3: The web server sends the requested webpage using HTTP.
A4: The web browser resolves the domain name using DNS.

Which is the correct order of execution of the above actions?

a)A4, A2, A1, A3
b)A1, A2, A3, A4
c)A4, A1, A2, A3
d)A2, A4, A1, A3

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Question 21Web Technology

Suppose you are using an HTML browser at a client machine C to access a static HTML webpage hosted in an HTTP server S. The page contains exactly one static embedded image which also resides at S. Assuming no web caching, which of the following is correct when you load the webpage along with the embedded image?

a)C needs to send at least 2 HTTP requests to S using two different TCP connections.
b)C needs to send at least 2 HTTP requests to S but a single TCP connection is sufficient.
c)A single HTTP request is sufficient without using any TCP connection from C to S.
d)A single HTTP request is sufficient using a single TCP connection from C to S.

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Question 22Networking

Which of the following is the Protocol Data Unit (PDU) for the application layer in the Internet stack?

a)Segment
b)Datagram
c)Message
d)Frame

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Question 23Software Engineering

Software goes through a phase in which errors are verified and studied on simulated user environments. This is referred to as-

a)Alpha testing
b)Beta testing
c)Gamma testing
d)Delta testing

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Question 24Algorithms

Suppose you are searching student data using student number as the key. Which of the following arrangement of the student data is suited for binary search?

a)Student data are arranged in the positions indicated by the student numbers' hash values
b)Student data are arranged randomly irrespective of the student numbers
c)Student data are arranged in ascending order of student numbers
d)Student data are arranged in the order of the cell addresses of the student numbers' locations.

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Question 25Database

A relationship is given below in an ER diagram. How many tables can be created (preferred) from below diagram?

Diagram not available online: ER diagram: instructor and student entities related by advisor relationship

a)One
b)Two
c)Three
d)No definite numbers

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Question 26Networking

Which of the following statements about connecting devices between LANs is accurate?

a)Gateway converts the protocols of the first to third layers of the OSI basic reference model
b)Bridge relays frames based on IP address
c)Repeater extends transmission distance by amplifying the signal between segments of the same type
d)Router relays frames based on MAC address

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Question 27Data Structures

Suppose you want to insert n elements into an empty linked list while maintaining the sorted order. What is the worst-case time complexity?

a)θ(n)
b)θ(n log n)
c)θ(1)
d)θ(n²)

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Question 28Database

Consider an Entity-relationship (ER) model where R is defined as a many-to-one relationship from entity set E1 to entity set E2. If E1 and E2 participate totally in R and cardinality of E1 is greater than the cardinality of E2, which of the following is true about R?

a)Every entity in E1 is associated with exactly one entity in E2
b)Some entity in E1 is associated with more than one entity in E2
c)Every entity in E2 is associated with exactly one entity in E1
d)Every entity in E2 is associated with at most one entity in E1

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Question 29Database

After a transaction completes successfully, the changes it has made to the database persist, even if there are system failures. This property of transaction is known as-

a)Atomicity
b)Consistency
c)Isolation
d)Durability

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Question 30Database

Consider the following Employee Table and the SQL query given:

id	Date	Work_hour
1	2020-10-18	8
1	2020-10-17	8
1	2020-10-16	9
2	2020-10-18	7
2	2020-10-16	8
3	2020-10-16	6

SELECT id, sum(work_hour) from Employee Where Work_hour>6 Group BY ID;

How many rows are returned by the SQL query?

a)3
b)4
c)2
d)0

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Question 31Networking

Suppose you need to assign IPv4 addresses to two computers of your company so that both computers belong to the subnet 255.255.255.240. Which of the following is a valid assignment?

a)172.16.5.14 and 172.16.5.17
b)172.16.5.17 and 172.16.5.29
c)172.16.5.29 and 172.16.5.33
d)172.16.5.33 and 172.16.5.4

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Question 32Database

Following table shows the delivery record of an online shop. Which of the SQL statements results in the largest value?

Product Id	Date	Quantity
F101	2020-10-17	3
H201	2020-10-17	2
F101	2020-10-16	1
H201	2020-10-16	2

a)SELECT AVG(Quantity) FROM Delivery Record WHERE Product id='F101'
b)SELECT COUNT (*) FROM Delivery Record
c)SELECT SUM (Quantity) FROM Delivery Record WHERE Date = '2020-10-16'
d)SELECT MAX (Quantity) FROM Delivery Record

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Question 33Mathematics

Which one of the following regular expressions represents the set of all binary strings with an odd number of 1's?

a)((0+1)*1(0+1)*1)*10*
b)(0*10*10*)*0*1
c)1*+(1*01*0)*1*
d)None

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Question 34Cyber Security

_____ is an assault on a service from a single source that floods it with so many requests that it becomes overwhelmed and is either stopped completely or operates at a significantly reduced rate.

a)Denial-of-service (DoS) attack
b)Spoofing attack
c)Cross-site scripting (XSS) attack
d)Buffer overflow attack

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Question 35Programming

What is the correct output of the following C program statements?

int array[]={6,7,8,9,0,1,2,4,5,6}, *p=array+5;
printf("%d\n",p[1]);

a)1
b)2
c)3
d)Compile Error

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Question 36Networking

What is the output power in watts of the following three-stage system?

Diagram not available online: Three-stage signal system: Pin=-12db through 40db, -35db, 25db blocks to Pout

a)0.431 Watt
b)0.5 Watt
c)18 Watt
d)0.0631 Watt

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Question 37Computer Architecture

Suppose the operating clock frequency of a typical CPU is 700 MHz and the number of clocks required for execution of three different instruction types are 4, 8, and 10. If the corresponding appearance rates of the instructions are 30%, 60% and 10%, respectively, how many MIPS does this CPU perform?

a)10
b)50
c)70
d)100

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