Question 1

Question 7Find errors (if any) in the following code and rewrite the code underlining each correction:x = int("Enter value of x:")
for in range[0, 10]:
    if x = y
        print("They are equal") 
    else:
        Print("They are unequal")

Accepted Answer

x = int("Enter value of x:") #Error 1
for in range[0, 10]: #Error 2
    if x = y #Error 3
        print("They are equal") 
    else:
        Print("They are unequal") #Error 4Error 1 — The input() function is missing from the code to prompt the user for input.Error 2 — The syntax of the range() function uses parentheses () rather than square brackets [] and the variable y is missing in the for loop declaration (for y in range(0, 10):).Error 3 — The comparison operator in the if statement has = (assignment) instead of == (equality comparison) and colon (:) is missing at the end.Error 4 — The print function should be written with a lowercase 'p' for proper syntax.The corrected code is:x = int(input("Enter value of x:"))
for y in range(0, 10):
    if x == y:
        print("They are equal") 
    else:
        print("They are unequal")

Question 2

Question 12What is the use of "w" in file handling?

Accepted Answer

In file handling, the "w" mode is used to open a file for writing. If the file exists, it will be overwritten. If the file does not exist, a new file will be created with the specified name.

Source: This question is from Practice Paper, Computer Science &mdash; Class 12, CBSE Board.
Key Concepts CoveredThis question tests your understanding of the following concepts from the chapter Practice Paper: Question, Use, File, Handling, Practice Paper, Computer Science. These are fundamental topics in Computer Science that students are expected to master as part of the CBSE Class 12 curriculum.A thorough understanding of these concepts will help you answer similar questions confidently in your CBSE examinations. These topics are frequently tested in both objective and subjective sections of Computer Science papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This QuestionRead the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to RememberWrite programs with proper indentation and comments.
Trace through your code with sample inputs to verify correctness.
Explain the logic behind each step of your solution.
Familiarise yourself with common library functions and methods.
Related Questions from Practice PaperQ1: Question 31 A departmental store "ABC" is considering maintaining their inventory using SQL to...
Q10: Question 24 What will the following snippet print? L5 = [ 1500 , 1800 , 1600 , 1200 , 1900 ] begin...
Q11: Question 25 Consider the following two SQL commands with reference to a table, named MOVIES, having...
Q13: Question 13 Rewrite the following SQL statement after correcting the error(s). Underline the...
Q14: Question 14 Write a function Push() which takes number as argument and add in a stack "MyValue"....
Practice more questions from Practice Paper &mdash; Computer Science, Class 12 CBSE

Question 3

Question 13Rewrite the following SQL statement after correcting the error(s). Underline the corrections made.INSERT IN STUDENT (RNO, MARKS)   
VALUE (5, 78.5);

Accepted Answer

INSERT IN STUDENT (RNO, MARKS) -- Error 1  
VALUE (5, 78.5); -- Error 2Error 1 — The correct syntax in SQL for inserting data into a table is "INSERT INTO", not "INSERT IN".Error 2 — The correct keyword used in SQL to specify the values being inserted into the table is "VALUES", not "VALUE".The corrected code is:INSERT INTO STUDENT(RNO, MARKS) 
VALUES (5, 78.5);

Question 4

Question 14Write a function Push() which takes number as argument and add in a stack "MyValue".SolutionMyValue = []

def Push(number):
    MyValue.append(number)
    print(number, "pushed to the stack.")

Push(5)
Push(10)
Push(15)Output5 pushed to the stack.
10 pushed to the stack.
15 pushed to the stack.

Accepted Answer

MyValue=[]defPush(number):MyValue.append(number)print(number,"pushed to the stack.")Push(5)Push(10)Push(15)Output5 pushed to the stack.10 pushed to the stack.15 pushed to the stack.

Question 5

Question 15Write the output of the following code:for i in range(5):
    print(i)

Accepted Answer

Output0
1
2
3
4

Question 6

Question 16Expand the following:(a) LIFO(b) FIFO

Accepted Answer

(a) LIFO — Last-In First-Out(b) FIFO — First-In First-Out

Source: This question is from Practice Paper, Computer Science &mdash; Class 12, CBSE Board.
Key Concepts CoveredThis question tests your understanding of the following concepts from the chapter Practice Paper: Question, Expand, Lifo, Fifo, Practice Paper, Computer Science. These are fundamental topics in Computer Science that students are expected to master as part of the CBSE Class 12 curriculum.A thorough understanding of these concepts will help you answer similar questions confidently in your CBSE examinations. These topics are frequently tested in both objective and subjective sections of Computer Science papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This QuestionRead the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to RememberWrite programs with proper indentation and comments.
Trace through your code with sample inputs to verify correctness.
Explain the logic behind each step of your solution.
Familiarise yourself with common library functions and methods.
Related Questions from Practice PaperQ1: Question 31 A departmental store "ABC" is considering maintaining their inventory using SQL to...
Q10: Question 24 What will the following snippet print? L5 = [ 1500 , 1800 , 1600 , 1200 , 1900 ] begin...
Q11: Question 25 Consider the following two SQL commands with reference to a table, named MOVIES, having...
Q13: Question 13 Rewrite the following SQL statement after correcting the error(s). Underline the...
Q14: Question 14 Write a function Push() which takes number as argument and add in a stack "MyValue"....
Practice more questions from Practice Paper &mdash; Computer Science, Class 12 CBSE

Question 7

Question 17Assertion (A): Program should check for Overflow condition before executing Push operation on stack and similarly check for Underflow condition before executing Pop operation.Reasoning (R): In stack, Underflow condition signifies that there is no element available in the stack while Overflow condition means no further element can be pushed in the stack.Both A and R are true and R is the correct explanation of A.Both A and R are true but R is not the correct explanation of A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is the correct explanation of A.ExplanationIt is essential to check for overflow conditions before executing a Push operation on a stack to ensure that the stack has enough space to accommodate the new element. Similarly, checking for underflow conditions before executing a Pop operation is necessary to prevent deleting elements from an empty stack. An underflow condition indicates an empty stack, while an overflow condition indicates a stack that has reached its maximum capacity and cannot accept more elements.

Question 8

Question 18Assertion (A): ('x' and 'y' or not 7) is a valid expression in Python.Reason (R): In Python, strings and numbers can be treated as Boolean values.Both A and R are true and R is the correct explanation of A.Both A and R are true but R is not the correct explanation of A.A is true but R is false.A is false but R is true.

Accepted Answer

Both A and R are true and R is the correct explanation of A.ExplanationIn the expression ('x' and 'y' or not 7), both 'x' and 'y' are non-empty string literals, hence they are evaluated as True, and 7 is a non-zero number, also evaluated as True. Therefore, this expression results in 'y'. In Python, when evaluating expressions in a Boolean context, such as conditions in if statements, non-empty strings, non-zero numbers, and non-None values are considered True, while empty strings, numeric zero (0), and None are considered False.

Question 9

Question 20Write push(rollno) and pop() method in Python:push(rollno) — to add roll number in Stackpop() — to remove roll number from StackSolutionstack = []

def push(rollno):
    stack.append(rollno)
    print("Roll number", rollno, "added to the stack.")

def pop():
    if not is_empty():
        rollno = stack.pop()
        print("Roll number", rollno, "removed from the stack.")
    else:
        print("Stack is empty, cannot perform pop operation.")

def is_empty():
    return len(stack) == 0

push(11)
push(12)
push(13)

pop()
pop()OutputRoll number 11 added to the stack.
Roll number 12 added to the stack.
Roll number 13 added to the stack.
Roll number 13 removed from the stack.
Roll number 12 removed from the stack.

Accepted Answer

stack=[]defpush(rollno):stack.append(rollno)print("Roll number",rollno,"added to the stack.")defpop():ifnotis_empty():rollno=stack.pop()print("Roll number",rollno,"removed from the stack.")else:print("Stack is empty, cannot perform pop operation.")defis_empty():returnlen(stack)==0push(11)push(12)push(13)pop()pop()OutputRoll number 11 added to the stack.Roll number 12 added to the stack.Roll number 13 added to the stack.Roll number 13 removed from the stack.Roll number 12 removed from the stack.

Question 10

Question 21Write the output of the following code with justification if the contents of the file "VIVO.txt" are:"Welcome to Python Programming!"F1 = open("VIVO.txt", "r")
size = len(F1.read())
print(size) 
data = F1.read(5)
print(data)

Accepted Answer

The given code opens a file named "VIVO.txt" in read mode and reads its entire content into a variable F1. It then calculates the length of this content using len() and prints the result, which is 30 characters long. However, when it tries to read the next 5 characters from the file using F1.read(5), no characters are left to read since the file pointer is at the end the file. As a result, data remains an empty string.Output30

Question 11

Question 23(a)Given is a Python string declaration:voice = "Python for All Learners"Write the output of:print(voice[20 : : -2])

Accepted Answer

Outputere l o otP
Explanationvoice[20 : : -2]: Starting from index 20, the expression goes till the end of the string in reverse order with a step size of -2.

Question 12

Question 23(b)Write the output of the code given below:d1 = {"A" : "Avocado", "B" : "Banana"} 
d2 = {'B' : 'Bag', 'C' : 'Couch'}
d2.update(d1)
print(len(d2))

Accepted Answer

Output3
ExplanationThe code initialize two dictionaries, d1 and d2, with key-value pairs. Then, it updates d2 with the key-value pairs from d1, overwriting the value of key 'B' in d2 with 'Banana' from d1 and adding the new key-value pair 'A' mapped to 'Avocado'. Finally, it prints the length of d2, which is 3 since d2 now has three key-value pairs after the update operation.

Question 13

Question 24What will the following snippet print?L5 = [1500, 1800, 1600, 1200, 1900] 
begin = 1
sum = 0
for c in range(begin, 4):
    sum = sum + L5[c]
    print(c, ':', sum)
    sum = sum + L5[0] * 10
    print("sum is", sum)

Accepted Answer

Output1 : 1800
sum is 16800
2 : 18400
sum is 33400
3 : 34600
sum is 49600
ExplanationThe given code initializes a list L5 with five elements. It then sets begin to 1 and sum to 0. The loop iterates for values 1, 2, and 3. In each iteration, the code adds the element at index c of L5 to sum, prints the c and updated sum, and then adds ten times the first element of L5 to sum and prints the value of sum.

Question 14

Question 25Consider the following two SQL commands with reference to a table, named MOVIES, having a column named Director:(a) Select Distinct Director from MOVIES;(b) Select Director from MOVIES;In which case will these two commands produce the same result?In which case will these two commands produce different results?

Accepted Answer

The two SQL commands will produce the same result when there are no duplicate values in the Director column of the MOVIES table. If every Director value in the table is unique, both commands will return the same set of distinct Director values.The two SQL commands will produce different results when there are duplicate values in the Director column of the MOVIES table. The first command with DISTINCT will only return unique Director values, omitting duplicates, whereas the second command without DISTINCT will return all Director values, including duplicates.

Question 15

Question 27In a database BANK, there are two tables with a sample data given below:Table: EMPLOYEEENoENameSalaryZoneAgeGradeDept1Mona70000East40A102Mukhtar71000West45B203Nalini60000East26A104Sanaj65000South36A205Surya58000North30B30Table: DEPARTMENTDeptDNameHOD10Computers120Economics230English5(a) To display ENo, EName, Salary and corresponding DName of all the employees whose age is between 25 and 35 (both values inclusive).(b) To display DName and corresponding EName from the tables DEPARTMENT and EMPLOYEE (Hint: HOD of DEPARTMENT table should be matched with ENo of EMPLOYEE table for getting the desired result).(c) To display EName, Salary, Zone and Income Tax (Note: Income tax to be calculated as 30% of salary) of all the employees with appropriate column headings.

Accepted Answer

Question 16

Question 28(b)Write a function reverseFile() in Python to read lines from text file 'TESTFILE.TXT' and display the file content in reverse order so that the last line is displayed first and the first line is displayed at the end.Solutiondef reverseFile():
    file = open('TESTFILE.TXT', 'r')
    lines = file.readlines()  
    line_count = len(lines)
    for i in range(line_count - 1, -1, -1):
        print(lines[i].strip()) 
reverseFile()OutputA marked difference will come in our country.
We all pray for everyone's safety
An apple a day keeps the doctor away.

Accepted Answer

defreverseFile():file=open('TESTFILE.TXT','r')lines=file.readlines()line_count=len(lines)foriinrange(line_count-1,-1,-1):print(lines[i].strip())reverseFile()OutputA marked difference will come in our country.We all pray for everyone's safetyAn apple a day keeps the doctor away.

Question 17

Question 31A departmental store "ABC" is considering maintaining their inventory using SQL to store data and maintain basic transactions. As a database manager, Mehak has to create two tables as Customer & Transaction:Table: CUSTOMERCNoCNAMEADDRESS101Richa JainDelhi102Surbhi SinhaChennai103Lisa ThomasBengaluru104Imran AliDelhi105Roshan SinghChennaiTable: TRANSACTIONDeptCNOAMOUNTTYPEDOTT0011011500Credit2017-11-23T0021032000Debit2017-05-12T0031023000Credit2017-06-10100410312000Credit2017-09-12T0051011000Debit2017-09-05(i) Identify the attribute best suited to be declared as a Primary key in customer table.(ii) Help Mehak to display details of all transactions of TYPE Credit from Table TRANSACTION.(iii) Mehak wants to display all CNO, CNAME and DOT (date of transaction) of those CUSTOMERS from tables CUSTOMER and TRANSACTION who have done transactions more than or equal to 2000 for the Balance Sheet.(iv) Mehak wants to display the last date of transaction (DOT) from the table TRANSACTION for the customer having CNO as 103. Which command will she use?

Accepted Answer

(i) The attribute best suited to be declared as a Primary Key in the CUSTOMER table is CNo (Customer Number). It uniquely identifies each customer in the table.(ii)SELECT * FROM TRANSACTION
WHERE TYPE = "Credit";Output+------+-----+--------+--------+------------+
| DEPT | CNO | AMOUNT | TYPE   | DOT        |
+------+-----+--------+--------+------------+
| T001 | 101 |   1500 | Credit | 2017-11-23 |
| T003 | 102 |   3000 | Credit | 2017-06-10 |
| T004 | 103 |  12000 | Credit | 2017-09-12 |
+------+-----+--------+--------+------------+
(iii)SELECT C.CNO, C.CNAME, T.DOT
FROM CUSTOMER C, TRANSACTION T
WHERE C.CNO = T.CNO AND T.AMOUNT >= 2000; Output+-----+--------------+------------+
| CNO | CNAME        | DOT        |
+-----+--------------+------------+
| 103 | LISA THOMAS  | 2017-05-12 |
| 102 | SURBHI SINHA | 2017-06-10 |
| 103 | LISA THOMAS  | 2017-09-12 |
+-----+--------------+------------+
(iv) Mehak will use "MAX()" function to display the last date of transaction (DOT) from the table TRANSACTION for the customer having CNO as 103.SELECT MAX(DOT) AS Last_Transaction_Date
FROM TRANSACTION
WHERE CNO = 103;Output+-----------------------+
| Last_Transaction_Date |
+-----------------------+
| 2017-09-12            |
+-----------------------+

Question 18

Question 34(b)The code given below accepts the roll number of a student and deletes the record of that student from the table STUDENT. The structure of a record of table Student is: RollNo — integer; Name — string; Class — integer; Marks — integer.Note the following to establish connectivity between Python and MySQL:• Username is root, Password is A5_b23.• The table exists in a MySQL database named SCHOOL.Write the following missing statements to complete the code:#Statement 1— to create the cursor object#Statement 2 — to execute the query#Statement 3 — to make the deletion in the database permanentimport mysql.connector as mysql
def sql data(): 
    conn=mysql.connect(host="localhost",
                        user="root",
                        password=" ",
                        database="school")
    ...............                                               #Statement 1
    rno=int(input("Enter Roll Number : "))
    qry="delete from student where RollNo={}".format(rno)
    ...............                                               #Statement 2 
    ...............                                               #Statement 3
    print ("Record deleted")

Accepted Answer

#Statement 1 — cursor = conn.cursor()#Statement 2 — cursor.execute(qry)#Statement 3 — conn.commit()The completed code is as follows:import mysql.connector as mysql
def sql_data(): 
    conn = mysql.connect(host = "localhost",
                        user = "root", 
                        password = "A5_b23",
                        database = "school")
    cursor = conn.cursor()  # Statement 1 - to create the cursor object
    rno = int(input("Enter Roll Number: "))
    qry = "DELETE FROM student WHERE RollNo={}".format(rno)
    cursor.execute(qry)  # Statement 2 - to execute the query
    conn.commit()  # Statement 3 - to make the deletion in the database permanent
    print("Record deleted")

Practice Paper

Section A 1 Mark Each

Section B 2 Marks Each

Section C 3 Marks Each

Section D 4 Marks Each

Section E 5 Marks Each