CBSE Class 11 Computer Science Important Questions 2026-27

This comprehensive question bank covers all important chapters of CBSE Class 11 Computer Science based on the latest syllabus. Practice these questions thoroughly for your exam preparation.

Chapter: Number System

Very Short Answer (1 mark)

Q1. Convert (25)₁₀ to binary.

25 / 2 = 12 remainder 1, 12 / 2 = 6 remainder 0, 6 / 2 = 3 remainder 0, 3 / 2 = 1 remainder 1, 1 / 2 = 0 remainder 1

Reading bottom to top: (25)₁₀ = (11001)₂

Q2. What is the decimal equivalent of (111)₂?

1x2² + 1x2¹ + 1x2⁰ = 4 + 2 + 1 = (111)₂ = (7)₁₀

Q3. What are the base values of binary, octal, and hexadecimal number systems?

Binary = base 2, Octal = base 8, Hexadecimal = base 16.

Short Answer (2-3 marks)

Q4. Convert (1011010)₂ to its octal and hexadecimal equivalents.

Binary to Octal (group in 3s from right):

001  011  010
 1    3    2

(1011010)₂ = (132)₈

Binary to Hexadecimal (group in 4s from right):

0101  1010
  5     A

(1011010)₂ = (5A)₁₆

Q5. Convert (AF3)₁₆ to decimal.

A(10) x 16² + F(15) x 16¹ + 3 x 16⁰ = 10 x 256 + 15 x 16 + 3 x 1 = 2560 + 240 + 3 = (AF3)₁₆ = (2803)₁₀

Q6. Find the 1's complement and 2's complement of (01011)₂.

1's complement: Flip all bits = 10100

2's complement: 1's complement + 1 = 10100 + 1 = 10101

Long Answer (5 marks)

Q7. Convert (245.75)₁₀ to binary.

Integer part (245): 245/2=122 R1, 122/2=61 R0, 61/2=30 R1, 30/2=15 R0, 15/2=7 R1, 7/2=3 R1, 3/2=1 R1, 1/2=0 R1

245 = (11110101)₂

Fractional part (0.75): 0.75 x 2 = 1.50 → 1 0.50 x 2 = 1.00 → 1

0.75 = (0.11)₂

(245.75)₁₀ = (11110101.11)₂

Chapter: Boolean Logic

Very Short Answer (1 mark)

Q8. Evaluate: 1 AND 0 OR 1

1 AND 0 = 0, then 0 OR 1 = 1

Q9. What is a universal gate? Name two universal gates.

A universal gate is a gate from which any other gate can be constructed. The two universal gates are NAND and NOR.

Q10. State De Morgan's first theorem.

(A.B)' = A' + B'. The complement of AND equals the OR of complements.

Short Answer (2-3 marks)

Q11. Draw the truth table for XOR gate.

A	B	A XOR B
0	0	0
0	1	1
1	0	1
1	1	0

XOR gives output 1 when inputs are different.

Q12. Simplify: A.B + A.B'

A.B + A.B'
= A(B + B')     [Distributive law]
= A(1)          [Complement law: B + B' = 1]
= A             [Identity law]

Q13. Verify De Morgan's first theorem using a truth table.

A	B	A.B	(A.B)'	A'	B'	A'+B'
0	0	0	1	1	1	1
0	1	0	1	1	0	1
1	0	0	1	0	1	1
1	1	1	0	0	0	0

Since (A.B)' = A'+B' in all cases, the theorem is verified.

Long Answer (5 marks)

Q14. Simplify: (A + B)(A + C) + A'BC

(A + B)(A + C) + A'BC
= AA + AC + AB + BC + A'BC     [Expanding]
= A + AC + AB + BC + A'BC      [AA = A]
= A(1 + C + B) + BC(1 + A')   [Taking common]
= A(1) + BC(1)                 [1 + X = 1]
= A + BC

Chapter: Python Basics

Very Short Answer (1 mark)

Q15. What is the output of print(type(5.0))?

<class 'float'>

Q16. What is the difference between = and == in Python?

= is the assignment operator (assigns a value), while == is the comparison operator (checks equality).

Q17. What will print(10 // 3) output?

Output: 3 (floor division gives the quotient without the remainder)

Short Answer (2-3 marks)

Q18. What is the output of the following code?

a = 10
b = 3
print(a / b)
print(a // b)
print(a % b)
print(a ** b)

3.3333333333333335
3
1
1000

/ gives float division, // gives floor division, % gives remainder, ** gives power.

Q19. Write a Python program to check if a year is a leap year.

year = int(input("Enter year: "))
if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0):
    print(year, "is a leap year")
else:
    print(year, "is not a leap year")

Q20. What is the difference between a list and a tuple in Python?

List	Tuple
Mutable (can be changed)	Immutable (cannot be changed)
Uses square brackets []	Uses parentheses ()
Slower	Faster
Example: [1, 2, 3]	Example: (1, 2, 3)

Long Answer (5 marks)

Q21. Write a Python program to print the Fibonacci series up to n terms.

n = int(input("Enter number of terms: "))
a, b = 0, 1

print("Fibonacci Series:")
for i in range(n):
    print(a, end=" ")
    a, b = b, a + b

Enter number of terms: 10
Fibonacci Series:
0 1 1 2 3 5 8 13 21 34

Q22. Write a Python program to count the frequency of each character in a string.

text = input("Enter a string: ")
freq = {}

for char in text:
    if char in freq:
        freq[char] += 1
    else:
        freq[char] = 1

print("Character frequencies:")
for char, count in freq.items():
    print(f"'{char}' : {count}")

Enter a string: hello
Character frequencies:
'h' : 1
'e' : 1
'l' : 2
'o' : 1

Chapter: Python Functions

Short Answer (2-3 marks)

Q23. What is the difference between actual parameters and formal parameters?

Formal parameters are the variables defined in the function definition (also called parameters). Actual parameters are the values passed to the function when it is called (also called arguments). Example: In def add(a, b), a and b are formal parameters. In add(5, 3), 5 and 3 are actual parameters.

Q24. What is the output?

def change(x):
    x = x + 10
    print("Inside:", x)

num = 5
change(num)
print("Outside:", num)

Inside: 15
Outside: 5

The value of num does not change because integers are immutable in Python. The function creates a new local variable x when it reassigns.

Q25. Explain default arguments with an example.

Default arguments are parameters that have pre-set values. If no argument is provided during the function call, the default value is used.

def greet(name, message="Hello"):
    print(f"{message}, {name}!")

greet("Aman")              # Uses default: Hello, Aman!
greet("Priya", "Welcome")  # Overrides: Welcome, Priya!

Default parameters must come after non-default parameters.

Long Answer (5 marks)

Q26. Write a Python function that takes a list of numbers and returns a tuple containing the sum, average, maximum, and minimum.

def analyze(numbers):
    total = sum(numbers)
    avg = total / len(numbers)
    mx = max(numbers)
    mn = min(numbers)
    return total, avg, mx, mn

marks = [85, 92, 78, 95, 88]
s, a, maximum, minimum = analyze(marks)
print(f"Sum: {s}")
print(f"Average: {a:.2f}")
print(f"Maximum: {maximum}")
print(f"Minimum: {minimum}")

Sum: 438
Average: 87.60
Maximum: 95
Minimum: 78

Chapter: Emerging Trends

Short Answer (2-3 marks)

Q27. What is IoT? Give two applications.

IoT (Internet of Things) is a network of physical devices embedded with sensors, software, and connectivity that enables them to collect and exchange data. Two applications: (1) Smart homes with connected devices like smart lights and thermostats that can be controlled via phone, (2) Healthcare wearables like fitness trackers that monitor heart rate and physical activity.

Q28. Differentiate between AI and Machine Learning.

AI	Machine Learning
Broader concept of intelligent machines	Subset of AI
Machines simulating human intelligence	Machines learning from data
Can be rule-based or learning-based	Always learning-based
Includes ML, NLP, Computer Vision	Includes supervised, unsupervised, reinforcement learning

Q29. What is cloud computing? Name its three service models.

Cloud computing is the delivery of computing services (servers, storage, databases, software) over the Internet on a pay-as-you-go basis. Three service models: IaaS (Infrastructure as a Service, provides virtual hardware), PaaS (Platform as a Service, provides development platforms), SaaS (Software as a Service, provides ready-to-use applications).

Long Answer (5 marks)

Q30. Explain any five emerging trends in IT with examples.

1. Artificial Intelligence (AI) - Machines that simulate human intelligence. Example: Virtual assistants like Siri and Google Assistant that understand voice commands.

2. Internet of Things (IoT) - Network of connected devices. Example: Smart agriculture systems using soil sensors for automated irrigation.

3. Cloud Computing - Computing services over the Internet. Example: Google Drive for cloud storage and Google Docs for online document editing.

4. Blockchain - Decentralized, immutable digital ledger. Example: Bitcoin cryptocurrency and supply chain tracking.

5. Big Data - Processing extremely large datasets for insights. Example: Social media companies analyzing user behavior for targeted advertising.

Chapter: Societal Impact of IT

Short Answer (2-3 marks)

Q31. What is the digital divide? List two causes.

The digital divide is the gap between people who have access to modern IT and those who do not. Two causes: (1) Economic inequality where poor people cannot afford devices and Internet, (2) Geographic location where rural areas lack Internet infrastructure.

Q32. What is e-waste? Why is proper disposal important?

E-waste is discarded electronic devices like old computers, phones, and TVs. Proper disposal is important because e-waste contains toxic materials like lead, mercury, and cadmium that can contaminate soil and water, causing serious health problems including brain damage, kidney damage, and cancer. India's E-Waste Management Rules, 2016 mandate proper recycling.

Q33. What is software piracy? Give two examples.

Software piracy is the unauthorized copying, distribution, or use of copyrighted software. Two examples: (1) Installing licensed software on more computers than permitted by the license, (2) Downloading cracked or keygen-activated software from the Internet.

Long Answer (5 marks)

Q34. Discuss the health impacts of excessive technology use and suggest preventive measures.

Physical Health Impacts:

1. Eye strain and headaches from prolonged screen time
2. Back and neck pain from poor posture while using computers
3. Carpal tunnel syndrome from repetitive typing and mouse use
4. Obesity from sedentary lifestyle and lack of physical activity

Mental Health Impacts:

1. Social media addiction leading to reduced productivity
2. Cyberbullying causing anxiety, depression, and low self-esteem
3. Sleep disorders from blue light exposure and late-night screen use

Preventive Measures:

1. Follow the 20-20-20 rule for eye care
2. Use ergonomic furniture and maintain proper posture
3. Take regular breaks every 30-45 minutes
4. Limit recreational screen time to 2 hours daily
5. Exercise regularly and maintain physical activity
6. Avoid using screens at least 1 hour before bedtime

Mixed Application-Based Questions

Q35. Write a Python function isPalindrome(text) that returns True if the text is a palindrome (reads the same forward and backward), and False otherwise.

def isPalindrome(text):
    text = text.lower()
    return text == text[::-1]

# Test
print(isPalindrome("madam"))    # True
print(isPalindrome("racecar"))  # True
print(isPalindrome("hello"))    # False
print(isPalindrome("Level"))    # True

True
True
False
True

Q36. Convert (1101.101)₂ to decimal and then to octal.

Binary to Decimal:

1x2³ + 1x2² + 0x2¹ + 1x2⁰ + 1x2⁻¹ + 0x2⁻² + 1x2⁻³
= 8 + 4 + 0 + 1 + 0.5 + 0 + 0.125
= 13.625

Decimal to Octal (integer part): 13 / 8 = 1 remainder 5, 1 / 8 = 0 remainder 1 → 15₈

Decimal to Octal (fractional part): 0.625 x 8 = 5.0 → 5

(1101.101)₂ = (13.625)₁₀ = (15.5)₈

Exam Strategy Tips

1. Number system questions - Show all working steps. Do not skip division/multiplication steps.
2. Boolean algebra - Name the law used in each simplification step.
3. Python programs - Write clean code with proper indentation. Add comments where helpful.
4. Truth tables - Draw complete tables with all input combinations.
5. Theory questions - Use tables for comparison questions and give Indian examples.
6. Functions - Always show the output alongside the code.
7. Time management - Spend 1.5 hours on theory (Section A, B, C) and 1 hour on programming (Section D).
8. Attempt all questions - There is no negative marking, so attempt every question.