2024 CBSE Class 12 Computer Science Question Paper with Detailed Solutions

As the CBSE board exams approach, students across the country are gearing up for one of the most important assessments of their academic journey. To help Class 12 Computer Science students prepare effectively, we have provided the 2024 CBSE Computer Science question paper along with detailed solutions. These solutions are designed to guide students through each question, offering clear explanations and insights to enhance their understanding and exam readiness.

Section A – Multiple Choice Questions (Each carries 1 mark)

1. True or False: While defining a function in Python, the positional parameters in the function header must always be written after the default parameters.
   SHOW ANSWER

   Answer: False. In Python, positional parameters must always come before any default parameters in the function signature.
2. The SELECT statement when combined with the ________ clause returns records without repetition:
   • (a) DISTINCT
   • (b) DESCRIBE
   • (c) UNIQUE
   • (d) NULL
   SHOW ANSWER

   Answer: (a) DISTINCT. The DISTINCT clause is used to return only distinct (different) values.

3. What will be the output of the following statement:

   print(16*5/4*2/5-8)

   • (a) -3.33
   • (b) 6.0
   • (c) 0.0
   • (d) -13.33
   SHOW ANSWER

   Answer: (b) 6.0. The expression evaluates to 6.0 following order of operations.

4. What possible output from the given options is expected to be displayed when the following Python code is executed?

   import random
   Signal = ['RED', 'YELLOW', 'GREEN']
   for K in range(2, 0, -1):
       R = random.randrange(K)
       print(Signal[R], end='#')

   • (a) YELLOW # RED #
   • (b) RED # GREEN #
   • (c) GREEN # RED #
   • (d) YELLOW # GREEN #
   SHOW ANSWER

   Answer: (b) RED # GREEN #. This code randomly selects indices from the Signal list and prints them.

5. In SQL, the aggregate function which will display the cardinality of the table is ________.
   • (a) sum()
   • (b) count()
   • (c) avg()
   • (d) sum(*)
   SHOW ANSWER

   Answer: (b) count(). The COUNT() function counts the number of rows or distinct values in a table.

6. Which protocol out of the following is used to send and receive emails over a computer network?
   • (a) PPP
   • (b) HTTP
   • (c) FTP
   • (d) SMTP
   SHOW ANSWER

   Answer: (d) SMTP. SMTP (Simple Mail Transfer Protocol) is used to send and receive emails.

7. Identify the invalid Python statement from the following:
   • (a) d = dict()
   • (b) e = {}
   • (c) f = []
   • (d) g = dict{}
   SHOW ANSWER

   Answer: (d) g = dict{}. It is invalid because Python uses parentheses to initialize a dictionary.

8. Consider the statements given below and choose the correct output from the given options:

   myStr = "MISSISSIPPI"
   print(myStr[:4] + "#" + myStr[-5:])

   • (a) MISS#SIPPI
   • (b) MISS#SIP
   • (c) MISS#IPPIS
   • (d) MISSI#IPPIS
   SHOW ANSWER

   Answer: (a) MISS#SIPPI. The slice [:4] gives “MISS” and [-5:] gives “SIPPI”.

9. Identify the statement from the following which will raise an error:
   • (a) print(“A”*3)
   • (b) print(5*3)
   • (c) print(“15” + 3)
   • (d) print(“15” + “13”)
   SHOW ANSWER

   Answer: (c) print(“15” + 3). This will raise a TypeError since strings and integers cannot be concatenated without explicit conversion.

10. Select the correct output of the following code:

    event = "G20 Presidency@2023"
    L = event.split(' ')
    print(L[::-2])

    • (a) [‘G20’]
    • (b) [‘Presidency@2023’]
    • (c) [‘G20’]
    • (d) ‘Presidency@2023’
    SHOW ANSWER

    Answer: (a) [‘G20’]. L[::-2] reverses the list and skips every other element.

11. Which of the following options is the correct unit of measurement for network bandwidth?
    • (a) KB
    • (b) Bit
    • (c) Hz
    • (d) Km
    SHOW ANSWER

    Answer: (b) Bit. Network bandwidth is measured in bits per second (bps).

12. Observe the given Python code carefully:

    a = 20
    def convert(a):
        b = 20
        a = a + b
    convert(10)
    print(a)

    • (a) 10
    • (b) 20
    • (c) 30
    • (d) Error
    SHOW ANSWER

    Answer: (b) 20. The value of a in the global scope is unchanged.

13. True or False: While handling exceptions in Python, the name of the exception has to be compulsorily added with the except clause.
    SHOW ANSWER

    Answer: False. In Python, a generic except block without specifying the exception type can be used.
14. Which of the following is not a DDL command in SQL?
    • (a) DROP
    • (b) CREATE
    • (c) UPDATE
    • (d) ALTER
    SHOW ANSWER

    Answer: (c) UPDATE. UPDATE is a DML (Data Manipulation Language) command, not a DDL command.

15. Fill in the blank: _________ is a set of rules that needs to be followed by the communicating parties in order to have a successful and reliable data communication over a network.
    SHOW ANSWER

    Answer: Protocol. A protocol is a set of rules for communication over a network.
16. Consider the following Python statement:

    F = open('CONTENT.TXT')

    Which of the following is an invalid statement in Python?

    • (a) F.seek(1, 0)
    • (b) F.seek(0, 1)
    • (c) F.seek(0, -1)
    • (d) F.seek(0, 2)
    SHOW ANSWER

    Answer: (c) F.seek(0, -1). Negative values for the second argument are invalid unless the file is opened in binary mode.

17. Assertion (A): A CSV file is a human-readable text file where each line has a number of fields, separated by a comma or some other delimiter.Reason (R): The writerow() method is used to write a single row in a CSV file.
    • (a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
    • (b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
    • (c) (A) is true, but (R) is false.
    • (d) (A) is false, but (R) is true.
    SHOW ANSWER

    Answer: (b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).

18. Assertion (A): The expression "HELLO".sort() in Python will give an error.Reason (R): The sort() method does not exist for strings in Python.
    • (a) Both (A) and (R) are true, and (R) is the correct explanation for (A).
    • (b) Both (A) and (R) are true, but (R) is not the correct explanation for (A).
    • (c) (A) is true, but (R) is false.
    • (d) (A) is false, but (R) is true.
    SHOW ANSWER

    Answer: (a) Both (A) and (R) are true, and (R) is the correct explanation for (A).

Section B – Very Short Answer Questions (Each carries 2 marks)

1. Rewrite the following code to correct syntactical errors:

   def max_num(L):
       max = L(0)
       for a in L:
           if a > max:
               max = a
       return max

   SHOW ANSWER

   Answer: The correct code is:

   def max_num(L):
       max = L[0]
       for a in L:
           if a > max:
               max = a
       return max

2. Differentiate between wired and wireless transmission.
   SHOW ANSWER

   Answer: Wired transmission uses cables like fiber optics or copper wires, whereas wireless transmission uses electromagnetic waves to transmit data.
3. Differentiate between URL and domain name with the help of an example.
   SHOW ANSWER

   Answer: A domain name is part of the URL. For example, in https://www.example.com, ‘example.com’ is the domain name, while the full URL specifies the exact page and protocol.
4. Consider the Python list: Listofnames = ["Aman", "Ankit", "Ashish", "Rajan", "Rajat"]. Write the output of:

   print(Listofnames[-1::-4:-1])

   SHOW ANSWER

   Answer: ‘Rajat’

5. Explain the concept of “Alternate Key” in a Relational Database Management System with an example.
   SHOW ANSWER

   Answer: An Alternate Key is a candidate key that is not the primary key. For example, in a table where ‘ID’ is the primary key, ‘Email’ can be an alternate key.
6. Write the full forms of:
   • (i) HTML
   • (ii) TCP
   SHOW ANSWER

   Answer: (i) HyperText Markup Language, (ii) Transmission Control Protocol

7. Write the output of the following code:

   subject = ['CS', 'HINDI', 'PHYSICS', 'CHEMISTRY', 'MATHS']
   short_sub(subject, 5)
   print(subject)

   SHOW ANSWER

   Answer: The output depends on the logic inside the short_sub function, which is not provided.

Section C – Short Answer Questions (Each carries 3 marks)

1. Differentiate between CHAR and VARCHAR data types in SQL with an example.
   SHOW ANSWER

   Answer: CHAR stores fixed-length strings, while VARCHAR stores variable-length strings. Example: CHAR(5) stores exactly 5 characters, while VARCHAR(5) can store up to 5 characters.
2. Consider the following tables – LOAN and BORROWER. How many rows and columns will be there in the natural join of these two tables?
   SHOW ANSWER

   Answer: There will be 2 rows and 3 columns in the natural join of LOAN and BORROWER tables.
3. Write a Python function LongLines() that reads the contents of a text file and displays lines with at least 10 words.
   SHOW ANSWER

   Answer:

   def LongLines():
       with open("LINES.TXT", "r") as file:
           for line in file:
               if len(line.split()) >= 10:
                   print(line)

4. Write the SQL queries for:
   • SELECT MIN(PRICE), MAX(PRICE) FROM COMPUTER;
   • SELECT COMPANY, COUNT(*) FROM COMPUTER GROUP BY COMPANY HAVING COUNT(COMPANY) > 1;
   SHOW ANSWER

   Answer: The two SQL queries return the minimum and maximum price from the COMPUTER table, and the count of products per company having more than 1 product, respectively.

5. Write a function EOReplace() in Python which accepts a list of numbers and increments all even numbers by 1 and decrements all odd numbers by 1.
   SHOW ANSWER

   Answer:

   def EOReplace(L):
       for i in range(len(L)):
           if L[i] % 2 == 0:
               L[i] += 1
           else:
               L[i] -= 1

Section D – Long Answer Questions (Each carries 5 marks)

1. Write a function Push_Cust() to push customer names staying in ‘Delux’ room type in a stack, and Pop_Cust() to pop and display customer names.
   SHOW ANSWER

   Answer: Implement the stack with Push_Cust() to add ‘Delux’ room customers and Pop_Cust() to remove and display customers.
2. An IT-based firm is planning to set up a network for its branches. Suggest an ideal layout to connect the branches and justify your choice.
   SHOW ANSWER

   Answer: A star topology can be ideal to connect the branches with the main hub as it is easy to maintain and troubleshoot.
3. Write a program in Python that defines and calls the following user-defined functions:
   • COURIER_ADD(): Takes values from the user and adds them to a CSV file courier.csv.
   • COURIER_SEARCH(): Takes the destination as input and displays all the courier records going to that destination.
   SHOW ANSWER

   Answer:

   import csv
   def COURIER_ADD():
       with open("courier.csv", "a", newline="") as file:
           writer = csv.writer(file)
           cid = input("Enter Courier ID: ")
           s_name = input("Enter Sender Name: ")
           source = input("Enter Source: ")
           destination = input("Enter Destination: ")
           writer.writerow([cid, s_name, source, destination])
   def COURIER_SEARCH(destination):
       with open("courier.csv", "r") as file:
           reader = csv.reader(file)
           for row in reader:
               if row[3] == destination:
                   print(row)

Section E – Internal Choice Questions (Each carries 4 marks)

1. The school has asked their estate manager Mr. Rahul to maintain the data of all the labs in a table LAB. Based on the data, identify the columns which can be considered as Candidate keys and write the degree and cardinality of the table.
   SHOW ANSWER

   Answer: Candidate keys: LABNO. Degree: 4. Cardinality: 5.
2. Write a user-defined function write_bin() to create a binary file called Cust_file.dat and store customer information (customer number, name, quantity, price, and amount).
   SHOW ANSWER

   Answer:

   import pickle
   def write_bin():
       with open("Cust_file.dat", "wb") as file:
           c_no = int(input("Enter Customer Number: "))
           c_name = input("Enter Customer Name: ")
           qty = int(input("Enter Quantity: "))
           price = float(input("Enter Price: "))
           amt = qty * price
           pickle.dump([c_no, c_name, qty, price, amt], file)