EMRS Tier-2 Computer Science Mock Paper 3

EMRS STAFF SELECTION EXAM (ESSE)-2025

ESSE 2025 Tier-2 Examination

TGT/PGT Computer Science (Mock Paper 3)

Time: 3 Hours Maximum Marks: 100

Instructions:

1. Section A consists of 40 Multiple Choice Questions (1 mark each).

2. Section B consists of 15 Descriptive Questions (4 marks each).

3. All questions are compulsory.

Section A: Multiple Choice Questions (40 × 1 = 40 Marks)

1. When two NOT gates are connected one after another, what is the resulting logic behavior?
(a) Inverter
(b) Buffer
(c) NAND gate
(d) NOR gate

Note: Two NOT operations cancel each other (A'') = A, so the output remains unchanged → acts as a buffer.

2. Which tool in Canva AI is used to turn a text-based document into an interactive quiz?

(a) Magic Media
(b) Brand Hub
(c) Magic Write (Generate Quiz)
(d) Animator

3. What is the purpose of a Virus Definition File (VDF) in antivirus software?
(a) Stores quarantined files
(b) Maintains known virus signatures for detection
(c) Tests suspicious files
(d) Encrypts user data

Note: VDF acts like a database that helps antivirus identify known threats.

4. If two tables with 10 and 5 records are combined using a cross join, how many rows will result?
(a) 15
(b) 5
(c) 10
(d) 50

Note: Cross join = all combinations → 10 × 5 = 50 rows.

5. What will be the output of modifying a list inside a tuple in Python?

(a) Error due to immutability
(b) (1, 2, [3, 4, 5])
(c) (1, 2, (7, 4, 5))
(d) (1, 2, [7, 4, 5])

Note: Tuple is immutable, but mutable elements (like lists) inside it can still change.

6. What is the correct binary representation of 99?
(a) (1100011)₂
(b) (1111011)₂
(c) (1101011)₂
(d) (1000011)₂

Note: 99 = 1100011 in binary.

7. Which SQL statement correctly inserts specific column values into a table?
(a) INSERT INTO Customer VALUES (...)
(b) INSERT Customer SET ...
(c) INSERT INTO Customer (CustomerID, Name, Product) VALUES (...)
(d) VALUES (...)

Note: Proper syntax requires specifying columns explicitly.

8. What will be the output after updating and summing dictionary values?

(a) 7
(b) 8
(c) 9
(d) 10

Note: After update → {'a':1, 'b':3, 'c':4} → sum = 8.

9. When is network snooping considered acceptable?
(a) By hackers
(b) For troubleshooting by administrators
(c) For spying
(d) For ad tracking

Note: Legitimate use includes monitoring networks for maintenance.

10. Which is NOT a valid file opening mode in Python?
(a) ab
(b) rw
(c) r+
(d) w+

Note: “rw” is not a valid mode in Python.

11. Which SQL command removes a table completely?
(a) alter
(b) delete
(c) drop
(d) update

Note: DROP deletes the entire table structure.

12. What range of values can be produced by randrange(100) + 1?
(a) 1 to 100
(b) 0 to 100
(c) 1 to 99
(d) 0 to 99

Note: randrange(100) → 0–99, +1 → 1–100.

13. What is DHCP used for?
(a) Address broadcasting
(b) Query-response system
(c) Acknowledgment system
(d) Automatic IP address assignment

Note: DHCP assigns IPs dynamically to devices.

14. What does cardinality represent in a database table?
(a) Number of rows (tuples)
(b) Number of tables
(c) Number of columns
(d) Number of constraints

Note: Cardinality = total number of records.

15. Which protocol maps IP addresses to physical addresses?
(a) RARP
(b) BOOTP
(c) ARP
(d) ICMP

Note: ARP translates IP → MAC address.

16. How many bits are present in an IPv4 address?
(a) 64
(b) 128
(c) 32
(d) 48

Note: IPv4 uses 32-bit addressing.

17. Which statement about first-generation computers is incorrect?
(a) High heat generation
(b) Vacuum tubes used
(c) Highly reliable
(d) Machine language used

Note: They were actually unreliable.

18. What is the role of buses in a computer system?
(a) Connect different hardware components
(b) Connect only RAM
(c) Run CMOS
(d) Increase CPU speed

Note: Buses enable communication between components.

19. Which of the following is considered a cybercrime?
(a) IPR violation
(b) Plagiarism
(c) Pornography
(d) All of the above

Note: All listed activities fall under cybercrime.

20. What is an ISP?
(a) A company providing internet access
(b) The web itself
(c) Local network
(d) Browser

Note: ISP gives users internet connectivity.

21. Which of the following is NOT a Python keyword?
(a) pass
(b) eval
(c) assert
(d) nonlocal

Note: eval() is a function, not a keyword.

22. What best defines blockchain technology?
(a) Centralized ledger
(b) Decentralized distributed ledger
(c) Class-based database
(d) None

23. Who developed ChatGPT?

(a) Google
(b) OpenAI
(c) Apple
(d) Microsoft

24. Which method writes a row into a CSV file in Python?
(a) writer
(b) writerow
(c) write
(d) writeline

Note: writerow() writes a single row.

25. What is the result of comparing 0.2 + 0.4 with 0.6 in Python?
(a) True
(b) False
(c) Error
(d) Depends

Note: Floating-point precision causes slight inaccuracy.

26. Which functions help in random file access?
(a) open & readlines
(b) seek & read
(c) seek & tell
(d) tell & read

Note: seek() moves pointer, tell() gives position.

27. Which device forwards data packets between networks?
(a) Modem
(b) Router
(c) Repeater
(d) USB

Note: Routers direct traffic between networks.

28. How do you correctly initialize an empty list in Python?
(a) emrs = list()
(b) emrs != list()
(c) emrs = list[]
(d) emrs = stacklist()

29. What is the output of the expression -

(a) -1024
(b) 32
(c) 0
(d) 1

30. Which is a proper net etiquette practice?
(a) Be precise, polite, credible
(b) Be ethical, precise, credible
(c) Be ethical, respectful, responsible
(d) Be secure, reliable, responsible

Note: Net etiquette focuses on respectful and responsible communication.

31.Which Python data structure internally uses hashing for storing elements?

(a) List
(b) Tuple
(c) Set
(d) Dictionary

Note: Dictionary is implemented using hash tables for fast key-based access.

32. Complete the SQL query to fetch employee codes where the address contains the word “GETSETSTUDY”:

(a) address LIKE GETSETSTUDY
(b) address = %GETSETSTUDY%
(c) address AS '%GETSETSTUDY_'
(d) address LIKE '%GETSETSTUDY%'

Note: % is a wildcard in SQL used with LIKE to match any sequence of characters before and after “GETSETSTUDY”.

33. Which of the following is an example of simplex mode communication?

(a) Single wire and two-sided communication
(b) Television
(c) Two-wire communication
(d) Walkie-talkie

Note: Simplex communication is one-way only. Television broadcasts signals only from sender to receiver.

34. What was the original name used for Microsoft Copilot when it was first launched?

(a) Microsoft Helper
(b) Bing AI
(c) Bing Chat
(d) Azure Assistant

Note: Microsoft Copilot was initially introduced as Bing Chat before being rebranded.

35. In _____ topology if there are n devices in a network, each device has n-1 ports for cables.

(a) Mesh
(b) Bus
(c) star
(d) ring

Note: Each device is connected to all other (n-1) ports per device

36. What is the purpose of Domain Name System Server ?

(a) For data encryption during transmission
(b) For network traffic regulation
(c) For converting domain names into IP addresses
(d) For secure connection establishment

37. How to mathematically add user input '45' to an integer 5 in python?

(a) "45"+5
(b) str("45"+5)
(c) int("45")+5
(d) "5" + str("45")

38. ___ and ____ are popular free and open source software tools.

(a) Matlab, Python
(b) Adobe Acrobat, Matlab
(c) MS-office, Microsoft Windows
(d) Libre Office, Mozilla Firefox

39. Why are polymorphic viruses harder to detect using traditional antivirus techniques?

(a) They do not contain executable code
(b) They modify their code or signature with each infection
(c) They remove antivirus programs
(d) They exist only in memory

Note: These viruses constantly change their appearance, making signature-based detection ineffective.

40. What error does the following code produce -

import math
num = -10
print(math.factorial(num))

(a) NameError
(b) TypeError
(c) ValueError
(d) ImportError

Section B: Descriptive Questions (15 × 4 = 60 Marks)

1. Explain Machine Learning training and testing process.

Machine Learning involves training a model using a dataset and then testing its performance on unseen data.

Training phase

- In the training phase, the model is given input data along with correct outputs (labels) so it can learn patterns and relationships.

- The model adjusts its internal parameters to minimize errors during this phase.

Testing phase

- In the testing phase, a separate dataset is used to evaluate how well the model performs on new data.

- This helps to check the accuracy and generalization ability of the model.

2. Explain iterative and branching steps in algorithm design.

Iterative steps -

Iterative steps refer to repeating a set of instructions until a condition is satisfied.

These are implemented using loops such as for and while.

For example, printing numbers from 1 to 10 using a loop is an iterative process.

Branching steps -

Branching steps involve making decisions based on conditions.

These are implemented using if, if-else, or elif statements.

For example, checking whether a number is even or odd is a branching process.

3. Write a program to simulate a basic login system in Python.

username = "admin"

password = "1234"

for i in range(3):

u = input("Enter username: ")

p = input("Enter password: ")

if u == username and p == password:

print("Login Successful")

break

else:

print("Invalid credentials")

else:

print("Account locked")

Points from the above program -

- The program stores a predefined username and password.

- It allows the user three attempts to enter correct credentials.

- If correct details are entered, login is successful.

- Else after three failed attempts, the account is locked.

4. How is IP address different from MAC address? Discuss briefly.

IP address -

- An IP address is a logical address assigned to a device on a network, used to identify it over the internet or a network.

- IP address can change depending on the network

- IP address works at the network layer

- IPv4: 32 bits, IPv6: 128 bits

Example - IP Address: 192.168.1.1 {numeric}

MAC address -

- A MAC address is a physical address assigned to a device’s network interface card (NIC) by the manufacturer.

- MAC address is usually fixed and unique.

- MAC address works at the data link layer.

- 48 bits

Example - MAC Address: 00:1A:2B:3C:4D:5E {hexadecimal}

5. Explain string immutability in Python.

- In Python, strings are immutable, which means their content cannot be changed after creation.

- Any modification to a string creates a new string instead of changing the original one.

For example, changing a character in a string is not allowed.

Example:

s = "hello"

s[0] = "H" # Error

To modify, a new string must be created:

s = "H" + s[1:]

6. Explain nested tuples with examples.

- A nested tuple is a tuple that contains another tuple as its element.

- It is used to store complex data structures.

- Nested tuples are also immutable like normal tuples.

Example:

t = (1, 2, (3, 4), 5)

Accessing elements:

print(t[2]) # (3, 4)

print(t[2][1]) # 4

7. Explain the importance of clock speed and cores in CPUs.

In CPUs, both clock speed and cores together determine overall CPU performance.

Clock speed -

Clock speed refers to the number of cycles a CPU can perform per second (measured in GHz).
Higher clock speed means faster execution of instructions.

CPU cores -

Cores refer to the number of processing units in a CPU.
More cores allow the CPU to perform multiple tasks simultaneously (multitasking).

8. Explain future challenges in IoT and smart technologies.

- Security and privacy issues due to large data collection from devices.

- Data management challenges because of huge volumes of generated data.

- Interoperability problems between different devices and platforms.

- Power consumption in maintaining always-connected devices.

- Ensuring reliable connectivity in remote or crowded networks is also a challenge.

9. Explain the importance of problem-solving skills in computer science.

- Problem-solving helps in breaking complex problems into smaller manageable parts.

- It is essential for designing efficient algorithms and programs.

- It improves logical thinking and decision-making abilities.

- It helps in debugging and optimizing code.

- Strong problem-solving skills lead to better software development.

10. Explain selection structures in Python with examples.

- Selection structures are used to make decisions based on conditions.

- They are implemented using if, if-else, and if-elif-else statements.

- These structures control the flow of program execution.

Example:

x = 10

if x > 0:

print("Positive")

else:

print("Negative")

Example with multiple conditions:

marks = 85

if marks >= 90:

print("A")

elif marks >= 75:

print("B")

else:

print("C")

11. Consider the following table named "Product", showing details of products being sold in a grocery shop. [1x 4 = 4 M]

(a) Create the table Product with appropriate data types and constraints.

CREATE TABLE Product (

PCode VARCHAR(10) PRIMARY KEY,

PName VARCHAR(50),

UPrice int,

Manufacturer VARCHAR(50)

);

(b) Identify the primary key in Product.

The primary key in the table "Product" is PCode.

(c) List the Product Code, Product name and price in descending order of their product name. If PName is the same, then display the data in ascending order of price.

SELECT PCode, PName, UPrice
FROM Product
ORDER BY PName DESC, UPrice ASC;

Output

| PCode | PName | UPrice |

| P01 | WASH POWDER | 120 |

| P02 | TOOTHPASTE | 54 |

| P04 | TOOTHPASTE | 65 |

| P03 | SOAP | 25 |

| P05 | SOAP | 38 |

| P06 | SHAMPOO | 245 |

(d) Add a new column Discount to the table Product.

ALTER TABLE Product

ADD COLUMN Discount float;

12. Explain the break and continue statements with examples.

Break statement -

The break statement is used to terminate the loop immediately when a condition is met.

Example:

for i in range(5):

if i == 3:

break

print(i)

Output: 0 1 2 (loop stops when i becomes 3)

Continue statement -

The continue statement is used to skip the current iteration and move to the next iteration of the loop.

Example:

for i in range(5):

if i == 3:

continue

print(i)

Output: 0 1 2 4 (value 3 is skipped)

NOTE : break stops the loop completely, while continue skips only one iteration.

13. What is the primary role of system bus? Why data bus is bidirectional while address bus is unidirectional?

- A system bus is a set of wires that connects the CPU, memory, and input/output devices.

- It acts as a communication channel for transferring data within the computer system.

Primary Role -

- The main role is to carry data, addresses, and control signals between different components.

- It ensures smooth communication and coordination between CPU, memory, and I/O devices.

Data bus

- The data bus carries actual data between CPU, memory, and devices.

- Data needs to move in both directions:

(1) From memory to CPU (reading data)

(2) From CPU to memory (writing data)

That's why the data bus is bidirectional.

Address Bus

- The address bus carries the address of memory locations.

- Only the CPU sends addresses to memory or I/O devices.

- Memory does not send addresses back to the CPU.

That's why the address bus is unidirectional.

Example -

CPU wants to read data from address 1000:

* CPU sends 1000 via address bus (one-way).
* Memory sends data (e.g., 25) via data bus (two-way).

14. Explain cyber crimes and preventive measures.

- Cyber crimes are illegal activities carried out using computers or the internet.

- They can lead to data loss and financial damage.

- Awareness and safe practices help in reducing cyber crimes

- Examples : hacking, phishing, identity theft, online fraud etc

Preventive measures:

* Use strong and unique passwords.

* Install antivirus and update software regularly.

* Avoid clicking on suspicious links or emails.

* Use secure networks and enable two-factor authentication.

15. What are cloud-based services. List & briefly explain some of the cloud-based services.

- Cloud-based services are services provided over the internet that allow users to access data, software, and resources without using local storage or hardware.

Below are some of the Cloud-based services -

* Platform as a Service (PaaS)

- It provides a platform for developers to build, test, and run applications online.

- It is commonly used for online coding without installing software.

- Example: Using online compilers or coding platforms.

* Infrastructure as a Service (IaaS)

- It provides virtual computing resources like servers, storage, and networking over the internet.

- Users can rent infrastructure instead of buying physical hardware.

- Example: Amazon Web Services (AWS).

* Software as a Service (SaaS)

- It provides software applications over the internet.

- Users can access software through a web browser without installation.

- Example: Google Maps.

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