Class 12 CBSE COMPUTER SCIENCE Sample Question Paper Answer sheet

Class XII
COMPUTER SCIENCE – NEW (083)
SAMPLE QUESTION PAPER (2021 – 22)
Max Marks: 70
Time: 3 hrs

General Instructions:

1. This question paper contains two parts A and B. Each part is compulsory.
2. Both Part A and Part B have choices.
3.  Part-A has 2 sections:
   • Section – I is short answer questions, to be answered in one word or one line.
   • Section – II has two case studies questions. Each case study has 4 case-based subparts. An examinee is to attempt any 4 out of the 5 subparts.
4. Part – B is Descriptive Paper.
5. Part- B has three sections
   • Section-I is short answer questions of 2 marks each in which two questions have internal options.
   • Section-II is long answer questions of 3 marks each in which two questions have internal options.
   • Section-III is very long answer questions of 5 marks each in which one question has question has internal option.

Part-A
Section-I
Select the most appropriate option out of the options given for each question. Attempt any 15 questions from question no 1 to 21.

1 . Identify the Python data types?
       a. “And” b. {‘name’: 26} c. [26, 24] d. (‘My’, ‘data’)       
Ans. a. String, b. Dictionary c. List d. Tuple

2 . A twisted pair cable is a pair of_________ wires that are twisted together to improve electromagnetic capability
Ans. Insulated

3 . Rita wants to display a column “TYPE” in table ACCOUNT. Write SQL statement to show which command she should use to select the column and give it an alias “EVENT TYPE”?  
Ans. SELECT TYPE as “EVENT TYPE” from ACCOUNT;

4 . Which is the default sorting order used in ORDER BY clause?
Ans. ASC

5 . Name the Python Library modules which need to be imported to invoke the following functions :
       i. writerow( )
      ii. dump ( )

Ans. 
       i . csv
      ii . Pickle

6 . _____ is the amount of data transmitted via a given communications Channel in a given unit of time.
Ans. bandwidth

7 . What is the value of c after executing these statements?
        c = 7//4
      a. 3         b. 1       c. 1.75        d. The statement is incorrect
Ans. b is correct.

8 . Which command is used to view a table structure?

Ans. DESC or DESCRIBE

9 . What is an Alternate Key?
Ans. A candidate key that is not the primary key is called an Alternate Key.
For example in Student table if there are two candidate keys – StudId and Stud_Name and StudId is the primary Key then Stud_Name is the alternate key.

10 . Give 2 mutable and 2 immutable types in Python?
Ans. Mutable: list, dictionary
          Immutable: string, int, tuples

11 . ___________ is a process of storing data into files and allows it to perform various tasks such as read, write, append, search and modify in files.
Ans. File Handling

12 . Which constraint makes sure that all values in a column satisfy a certain criteria?
Ans. CHECK

13 . Write an SQL query to print details of workers excluding FIRST_NAME, “Ronit” and “Nitin” from WORKER table.

Ans. Select * from WORKER where FIRST_NAME not in  (‘Ronit’ ‘Nitin’);

14 . Which one of these is output of these Python commands? 
           L = [1,3,5,3,1]
           print (L.index(3),L.count(3)))
                a) 12
                b) 1 2
                c) 22
               d) 2 2
Ans. b

15 . What is the output of these Python commands? 
           A = (1,2,(3,4),5)
          print (len(A), A[2])
Ans. 4 (3, 4)

16 . __________command will test the connectivity between two host
Ans.  Ping

17 . What is the output of the following commands?

          score =20
          while score > 1:
             score=score//2-1
             print(score,end=’ ‘)
Ans. 9 3 0

18 . Ronit downloaded a harmless looking game from internet. Soon his computer started abnormal functioning. Sometimes it would restart by itself and sometimes it would stop different applications running on it. Which of the following options out of (i) to (iv), would have caused the malfunctioning of the computer?
         a. Trojan Horse
         b. Spam Mail
         c. Computer Bacteria
        d. Hardware breakdown
Ans. a. Trojan Horse

19 . To read 4th line from text file, which of the following statement is true? 
             a. dt = f.readlines();print(dt[3])
             b. dt=f.read(4) ;print(dt[3])
             c. dt=f.readline(4);print(dt[3])
             d. All of these
Ans. a. dt = f.readlines();print(dt[3])

20 . Which protocol is used for transferring files from one computer to another?
Ans. FTP

21 . Stack is _____ data structure. 
           a. FIFO
           b. LIFO
           c. POP
           d. None of above.
Ans. b. LIFO

Section-II
Both the Case study based questions(22 & 23) are compulsory. Attempt any 4 sub parts from each question. Each sub question carries 1 mark.

22 .Observe the following table carefully and Answer the following questions. 

Table: Store

Item code	Item	Qty	Rate
10	Gel pen classic	1150	25
11	Sharpener	1500	10
12	Ball pen 0.5	1600	12
13	Eraser	1600	5
15	Ball pen 0.25	800	20

       a. In the above table, can we have Qty as primary key?
       b. What is the cardinality and degree of the above table?
       c. Write a query to display the structure of table store from Mall Database.
       d. Give the output of following query.
                 Select distinct Item from Store;
       e. If we want to display maximum rate in store from Mall Database. Which command will be use the following:
                a. Select min(rent) from resort;
                b. Select minimum(rent) from mall;
                c. Select min(rent) from mall;
                d. Select minimum(rent) from resort;
Ans.
        a. We cannot use Qty as primary key because there is a duplication of values and primary key value cannot be duplicate.
        b. Degree =4
            Cardinality = 5
        c. Describe store;
        d.

Item
Gel pen classic
Sharpener
Ball pen 0.5
Eraser

        e. a. Select min(rent) from resort;

23 . Nyra has a branch1.csv file which has the name, class and section of students. She receives a branch2.csv which has similar details of students in second branch. She is asked to add the details of branch2,csv into branch1.csv. As a programmer, help her to successfully execute the given task.

__a__ csv
file = open('branch1.csv', __b__ , newline="");
writer = csv. __c__ (file)
with open('branch2.csv','r') as csvfile:
data = csv.reader(csvfile)
for row in data:
writer.writerow(__d__)
file. __e__ ()

a. Name the command she should use to include csv library.
b. In which mode she should open the file to add data into the file
c. Name the csv method which returns the object responsible for converting user’s data into delimited
strings
d. Fill in the blank with the information that needs to be written to csvfile.
e. Fill in the blank to close the file.

Ans.

import csv
file = open('branch1.cs','a', newline="");
writer = csv.writer(file)
with open('branch2.csv','r') as csvfile:
data = csv.reader(csvfile)
for row in data:
writer.writerow(row)
file.close()

Part-B
Section-I

24 . Rewrite the following code in python after removing all syntax error(s). Underline each correction done in the code.

c=dict{}
n=input("enter total number")
i=1
while I <= n:
  a=input("enter place")
  b=input("enter number")
  c[a]=b
  i=i+1
print("place","\t","number")
for i in c:
  print i + "\t"+ c[i]

Ans.

c=dict{}
n=input("enter total number")
i=1
while I <= n:
  a=input("enter place")
  b=input("enter number")
  c[a]=b
  i=i+1
print("place","\t","number")
for i in c:
  print i + "\t"+ c[i]

25 . Give full forms of the following? 
             1. VOIP,      2. ARPANET,      3. SMTP,       4. RFID
Ans. 
         1. VOIP- Voice over Internet Protocol
        2. ARPANET – Advanced Research Projects Agency Network)
        3. SMTP- Simple Mail Transfer Protocol
        4. RFID-Radio Frequencies Identification

26 . Define String in Python?     
Ans.  String in Python is formed using a sequence of characters. Value once assigned to a string cannot be modified because they are immutable objects. String literals in Python can be declared using double quotes or single quotes.
        Example:
                print(“Simply Coding”)
                print(‘ Simply Coding ‘)

27 . Find and write the output of the following python code:   

a=['Cat','Dog','cat','Dog']
def manip(f1):
  animal={}
  for index in f1:
    if index in animal:
      animal [index] += 1
    else:
      animal[index] =1
  return(animal)
ret = manip(a)
print (ret)
print (len(ret))

Ans. {‘Cat’: 1, ‘Dog’: 2, ‘cat’: 1}
          3

28 . What is the difference between packet switching and circuit switching techniques?
Ans.Circuit Switching In this, first complete physical connection between two computers is established. After that data is transmitted from the source computer to the destination computer.
       e.g. In telephone call, circuit switching is used.
Packet Switching In this, data is divided into packets. And they are sent without any reservation of resources. Each packet has destination address and transmission is done by intermediate routers. It makes it less reliable but there is less wastage of resources.

29 . Which option is NOT the possible outcome(s) executed from the following code?

import random
def main():
  p = "MY PROGRAM"
  i = 0
  while p[i] != "R":
    l = random.randint(0,3) + 5
    print (p[l],end ="_")
    i += 1
main()