# Class 12 Computer Science answer key 2024 – A comprehensive Solutions

In this article, I will discuss Class 12 Computer Science Answer Key 2024. The class 12 Computer Science exam was held on 02.04.2024. The paper was moderate. So let us begin.

Topics Covered

## Class 12 Computer Science Answer Key 2024

There are 5 sections.

## Section A – Class 12 Computer Science Answer Key 2024

[1] State True or False:

While defining a function in Python, the positional parameters in the function header must always be written after the default parameters.

[2.] The SELECT statement when combined with ____ clause, returns records without repetition

(a) DISTINCT

(b) DESCRIBE

(c) UNIQUE

(d) NULL

[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

[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

[5.] In SQL, the aggregate function which will display the cardinality of the table is____

(a) Sum()

(b) Count(*)

(c) Avg()

(d) Sum(*)

[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

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

``````myStr=”MISSISSIPPI”

print( myStr[:4] + “#”+myStr [-5:])``````

(a) MISSI#SIPPI

(b) MISS#SIPPI

(c) MISS#IPPIS

(d) MISSI#IPPIS

[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”)

[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’

[11.] Which of the following options is the correct unit of measurement for network bandwidth?

(a) KB

(b) Bit

(c) Hz

(d) Km

12. Observe the given Python code carefully:

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

Select the correct output from the given options:
(a) 10

(b) 20
(c) 30
(d) Error

[13.] State whether the following statement is True or False

While handling exceptions in Python, name of the exception has to be compulsorily added with except clause.

[14.] Which of the following is not a DDL command in SQL?
(a) DROP
(b) CREATE
(c) UPDATE
(d) ALTER

[15.] Fill in the blanks:

_________ 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.

[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)

Q17 and 18 are ASSERTION AND REASONING based questions. Mark the correct choice as

(a) Both A and R are true and R is the correct explanation for A
(b) Both A and R are true and R is not the correct explanation for A
(c) A is True but R is False
(d) A is false but R is True

[17.] Assertion (A): CSV File is a human readable file where each line has a number of fields, separated by comma or some other delimiter.

Reason (R): writerow() function is used to write a single row in a CSV file.

[18.] Assertion (A) : The expression “HELLO”.sort() in Python will give an error.

Reason (R): sort() does not exist as a method/function for strings in python.

## Section B – Class 12 Computer Science Answer Key 2024

[19.] (A) (i) Expand the following terms: XML, PPP

(ii) Given one difference point between circuit switching and packet switching.

OR

(B) (i) Define the term web hosting.

(ii) Name any two web browsers.

[20.] The code given below accepts five numbers and displays whether they are even or odd. Observe the following code and rewrite it after removing all syntax and logical errors:

``````def EvenOdd()
for i in range(5):
num=int(input("Enter a number")
if num/2==0:
print("Even")
else:
print("Odd")
EvenOdd()``````

Ans.:

``````def EvenOdd(): # Colon at the end of statement
for i in range(5):
num=int(input("Enter a number")) # Closing bracket missing
if num%2==0: # The operator needs to be changed
print("Even")
else:
print("Odd") # Indentation
EvenOdd()``````

[21.] (A) Write a user-defined function in Python named showGrades(S) which takes the dictionary S as an argument. The dictionary, S contains Name:[Eng, Math, Science] as key:value pairs. The function displays the corresponding grade obtained by students according to the following grading rules:

For Example, Consider the following dictionary:

S={“AMIT”:[92,86,64],”NAGMA”:[65, 42, 43],”DAVID”:[92, 90, 88]}

The output should be:

AMIT – B

NAGMA – C

DAVID – A

Ans.:

``````def showGrades(S):

for i in S:
s=0
for j in S[i]:
s+=j
avg=s/3
if avg>=90:
elif avg>=60 and avg<90:
elif avg<60:
S={"AMIT":[92,86,64],"NAGMA":[65, 42, 43],"DAVID":[92, 90, 88]}

(B) Write a user-defined function in Python named Puzzle(W,N) which takes the argument W as an English word and N as an integer and returns the string where every Nth alphabet of the word W is replaced with an underscore(“-“).

For example: if W contains the word “TELEVISION” and N is 3, then the function should return the string “TE_EV_SI_N”. Likewise for the word “TELEVISION” if N is 4, then the function should return “TEL_VIS_ON”.

Ans.:

``````def Puzzle(W,N):
l=list(W)
s1=''
for i in range(0,len(l)):
if i!=0 and (i+1)%N==0:
s1+='_'
else:
s1+=W[i]
return str(s1)
w=input("Enter English Word:")
n=int(input("Enter n to replace:"))
print(Puzzle(w,n))``````

[22.] Write the output displayed on the execution of the following Python code:

``````LS=["HIMALAYA","NILGIRI","ALASKA","ALPS"]
D={}
for S in LS:
if len(S)%4==0:
D[S]=len(S)
for K in D:
print(K,D[K],sep="#")``````

[23.] (A) Write a Python statement for each of the following tasks using built-in functions/methods only:

(i) To remove an item whose key is “NISHA” from a dictionary named Students.

For example, if the dictionary Students contains {“ANITA”:90,”NISHA”:76,”ASHA”:92}

(ii) To display the number of occurrences of the substring “is” in a string named message.

For example, if the string message contains “This is his book”, then the output will be 3.

OR

(B) A tuple named subject stores the names of different subjects. Write the Python commands to convert the given tuple to a list and thereafter delete the last element of the list.

Ans.:

``````subject=("English","Physics","Chemistry","Maths","Biology","Computer Science")
l=list(subject)
l.pop()
print(l)``````

[24.] (A) Ms. Veda created a table named Sports in a MySQL database, containing columns Game_Id, P_Age and G_Name.

After creating the table, she realized that the attribute, Category has to be added. Help her to write a command to add the Category column. Thereafter, write the command to insert the following record in the table:

OR

(B) Write the SQL commands to perform the following tasks:

1. View the list of tables in the database Exam
2. View the structure of the table Term1

[25] Predict the output of the given code:

``````def callon(b=20,a=10):
b=b+a
a=b-a
print(b,'#',a)
return b
x=100
y=200
x=callon(x,y)
print(x,'@',y)
y=callon(y)
print(x,'@',y)``````

## Section C – Class 12 Computer Science Answer Key 2024

[26] Write the output on execution for the following Python code:

``````S="Racecar Car Radar"
L=S.split()
for W in L:
x=W.upper()
if x==x[::-1]:
for I in x:
print(I, end='*')
else:
for I in W:
print(I,end='#')
print()``````

[27] Consider the table ORDERS given below and write the output of the SQL queries that follow.

(I) SELECT ITEM, SUM(QTY) FROM ORDERS GROUP BY ITEM;

(ii) SELECT ITEM, QTY FROM ORDERS WHERE ORDATE BETWEEN ‘2023-11-01’ AND ‘2023-12-31’;

(iii) SELECT ORDNO, ORDATE FROM ORDERS WHERE ITEM = ‘WHEAT’ AND RATE>=60;

[28] (A) Write a user-defined function in Python named showLines() which reads the contents of a text file named STORY.TXT and displays every sentence in a separate line.

Assume that a sentence ends with a full stop (.), a question mark (?), or an exclamation mark(!).

For example, if the content of file STORY.TXT is as follows:

Our parents told us that we must eat vegetables to be healthy. And it turns out, our parents were right! So, what else did our parents tell?

Then the function should display the file contents as follows:

`Our parents told us that we must eat vegetale to be healthy. And it turns out, our parents were right!So, what else did our parents tell?`

Ans.:

Method 1:

``````def showInLines():
f=open("story.txt")
sentence=[]
sentence1=[]
sentence2=[]
for i in l:
if i=='.':
idxdt=l.index(i)
sentence.append(l[:idxdt+1])
elif i=='!':
idxe=l.index(i)
sentence1.append(l[idxdt+1:idxe+1])
elif i=='?':
idxq=l.index(i)
sentence2.append(l[idxe+1:idxq+1])
for i in sentence:
print(i)
for i in sentence1:
print(i)
for i in sentence2:
print(i)
showInLines()
``````

Method 2:

``````def showLines():
f=open("story.txt")
sentence=[]
cur_sen=''
for i in x:
cur_sen+=i
if i in ['.','?','!']:
sentence.append(cur_sen.strip())
cur_sen=''
if cur_sen:
sentence.append(cur_sen.strip())
for i in sentence:
print(i)
showLines()``````

OR

(B) Write a function, c_words() in Python that separately counts and displays the number of uppercase and lowercase alphabets in a text file, words.txt.

Ans.:

``````def c_words():
f=open("story.txt")
uc=0
lc=0
for i in x:
if i.isupper():
uc+=1
if i.islower():
lc+=1
print("Uppercase Letters:",uc)
print("Lowercase Letters:",lc)
c_words()``````

[29] Consider the table projects given below:

Table: Projects

Based on the given table, write SQL queries for the following:

(i) Add the constraint, primary key to column P__id in the existing table Projects.

(ii) To change the language to Python of the project whose id is P002.

(iii) To delete the table Projects from MySQL database along with its data.

[30] Consider a list named Nums which contains random integers:

Write the following user defined functions in Python and perform the specified operations on a stack named BigNums.

(i) PushBig(): It checks every number from the list Nums and pushes all such numbers which have 5 or more digits into the stack, BigNums.

(ii) PopBig(): It pops the numbers from the stack, BigNums, and displays them. The function should also display “Stack Empty” when there are no more numbers left in the stack.

For example: If the list Nums contains the following data:

Nums=[213,10025,167,254923,14,1297653,31498,386,92765]

Then on execution of PushBig(), the stack BigNums should store:

[10025, 254923, 1297653, 311498, 92765]

And on execution of PopBig(), the following output should be displayed:

92765
31498
1297653
254923
10025
Stack Empty

Ans.:

``````Nums=[213,10025,167,254923,14,1297653,31498,386,92765]
BigNums=[]
def PushBig():
for i in Nums:
if i>=10000:
BigNums.append(i)
return BigNums
def PopBig():
if BigNums==[]:
return "Stack is empty"
else:
return BigNums.pop()

print(PushBig())
while True:
if BigNums!=[]:
print(PopBig())
else:
break
if BigNums==[]:
print("Stack Empty")``````

## Section D – Class 12 Computer Science Answer Key 2024

[31] Consider the tables Admin and Transport given below:

Table: Transport

Write SQL queries for the following:

(i) Display the student name and their stop name from the tables Admin and Transport.

(ii) Display the number of students whose S_type is not known.

(iii) Display the details of the students whose names starts with ‘V’

(iv) Display student id and address in alphabetical order of student name from the table admin

Ans.:

[32] Sangeeta is a Python programmer working in a computer hardware company. She has to maintain the records of the peripheral devices. She created a csv file named Peripheral.csv, to store the details. The structure of Peripheral.csv is:

[P_id, P_name, Price]

where

P_id is Peripheral devices ID (integer)

P_name is Peripheral device name (String)

Price is Peripheral device price (integer)

Sangeeta wants to write the following user-defined functions:

Add_Devices(): to accept a record from the user and add it to a csv file, Peripheral.csv

Count_Device(): To count and display number of peripheral devices whose price is less than 1000.

Ans.:

``````import csv
P_id=int(input("Enter Peripheral id:"))
P_name=input("Enter Peripheral Name:")
price=float(input("Enter price:"))
f=open("Peripheral.csv","a",newline='')
wo=csv.writer(f)
wo.writerow([P_id,P_name,price])
f.close()
def Count_device():
cnt=0
f=open("Peripheral.csv","r")
l=list(ro)
for i in l:
if i[2]<1000:
cnt+=1
print("Number of devices:",cnt)
Count_device()``````

## Section E – Class 12 Computer Science Answer Key 2024

[33] Infotainment Ltd. is an event management Ltd. is an event management company with its prime office located in Bengaluru. The company is planning to open it new division at three different locations in Chennai named as – Vajra, Trishula and Sudershana.

You, as a networking expert, need to suggest solutions to the questions in part (i) to (v), keeping in mind the distances and other given parameters.

Distances between various locations:

Number of computers installed at various locations:

(i) Suggest and draw the cable layout to efficiently connect various locations in the Chennai division for connecting the digital devices.

(ii) Which block in Chennai division should host the server? Justify your answer.

(iii) Which fast and effective wired transmission medium should be used to connect the prime office at Begaluru with the Chennai division?

(iv) Which network device will be used to connect the digital devices within each location of the Chennai division so that they may communicate with each other?

(v) A considerable amount of data loss is noticed between different loc

Ans.:

(i)

(ii) Vajra block in Chennai division shoud host server because it has maximum number of computers installed, and according to 80:20 rule the server should be placed in the room where maximum number computers are installed.

(iii) Fibre optical cable should be used to connect the prime office at Bengaluru with the Chennai location.

(iv) Switch will be used to connect the digital devices within each location of Chennai division.

(v) Repeater should be installed to refresh the data loss during transmission to and from different locations of Chennai division.

[34] (A) (i) Differentiate between ‘w’ and ‘a’ file modes in Python.

(ii) Consider a binary file, items.dat, containing records stored in the given format:

{item_id:[item_name, amount]}

Write a function, Copy_new(). that copies all records whose amount is greater than 1000 from items.dat to new_items.dat.

Ans.:

(i)

(ii)

``````def Copy_new():
d1={}
f=open("items.dat","rb")
while True:
try:
for i in dt:
if dt[i][1]>1000:
d1[i]=dt[i]
except EOFError:
break
f.close()

f=open("items.dat","wb")
pickle.dump(d1,f)
f.close()
Copy_new()``````

OR

(B) (i) What is the advantage of using with clause while opening a data file Python? Also give syntax of with clause.

(ii) A binary file EMP.DAT has the following structure:

[Emp_Id, Name, Salary]

where

Emp_Id : Employee id

Name: Employee Name

Salary: Employee Salary

Write a user defined function, disp_Detail(), that would read the contents of the file EMP.DAT and display the details of those employees whose salary is below 25000.

Ans.:

(i) The with clause automatically closes the file after nested block of code. It guarantees to close the file no matter how the nested block exists even exception occurs before the end of the block, the with statement will handle it and close the file.

(ii)

``````import pickle
def disp_Detail():
f=open("emp.dat","rb")
while True:
try:
for i in range(len(dt)):
if dt[2]<25000:
print(dt[i],end=" ")
print()
except EOFError:
break
disp_Detail()``````

[35] (A) (i) Define cartesian product with respect to RDBMS.

(ii) Sunil wants to write a program in Python to update the quantity to 20 of the records whose item code is 111 in the table named shop in MySQL database named Keeper.

The table shop in MySQL contains the following attributes:

• Item_code: Item code (Integer)
• Item_name: Name of item (String)
• Qty: Quantity of item (Integer)
• Price: Price of item (Integer)

Consider the following to establish connectivity between Python and MySQL:

• Host : localhost

Ans.:

(i) Cartesian products refers to the product of two tables of all possible concatenations are formed of all rows of both tables.

(ii)

``````import mysql.connector as m
cr=cn.cursor()
cr.execute("update shop set qty=20 where item_code =111")
cn.commit()``````

OR

(B) (i) Give any two features of SQL.

(ii) Sumit wants to write a code in Python to display all the details of the passengers from the table flight in MySQL database, Travel. The table contains the following attributes:

F_code : Flight code (String)

F_name: Name of flight (String)

Source : Departure city of flight (String)

Destination : Destination city of flight (String)

Consider the following to establish connectivity between Python and MySQL:

• Host: localhost

Ans.:

(i)

• Speed
• Ease of use
• Cost
• Query Language
• Portability
• Data Types
• Scalability and Limits
• Localization

(ii)

``````import mysql.connector as my
cn=my.connect(host='localhost',user='root',passwd='airplane',database='school')
cur=cn.cursor()
cur.execute("select * from shop")
dt=cur.fetchall()
for i in dt:
print(i)
cn.close()``````