KENDRIYA VIDYLAYA SANGATHAN JAMMU REGION

I PREBOARD EXAMINATION 2020-21

CLASS: XII
Computer Science – 083
MARKING SCHEME
Maximum Marks: 70 Time Allowed: 3 hours
Part – A
Section - I
1 a) (I) and (iv) 1
2 [“N”] 1
3 F=open("ABC.TXT","r") 1
4 False 1
5 20,40,60,80 1
6 dict_keys(['amit', 'vishal']) 1
7 It will show error tuple is immutable. 1
8 gcd (x , y ) which is a part of math module in python 1
9 FTP or HTTP 1
10 The gaining of unauthorized access to data in a system or computer is termed as 1
hacking. It can be classified in two ways:
(i) Ethical Hacking (ii)Cracking
11 Select name from teacher where subject is Null; 1
12 Count(*) will count rows where as count(name) will count name column only which is 1
having one null value.
13 Where is used apply condition in query, where as having is used only with group. 1
14 Alter table student add marks int(3) 1
15 Bluetooth, infra red 1
16 tuple 1
17 [10, 12, 43, 39, 10, 12, 43, 39, 10, 12, 43, 39] 1
18 Desc teacher; 1
19 (C) 1
20 The BETWEEN operator selects values within a given range. 1
21 (c) Trojan Horse 1
22 (i) P_ID is Best suitable primary key 1
1 mark for correct
1
(ii) Degree = 4, cardinality = 5
1
(iii) Insert into PRODUCT values(‘WP01’, ‘Washing Powder’,’null’,’150);
(iv) a 1
(v) show tables
1
23 (a) pickle 1
(b) wb 1
(c) rb 1
(d) file2.close() 1
(e) C 1
24 51 2
True
1 mark for each correct answer.
25 Hub forwards the message to every node connected and create a huge traffic in the 2
network hence reduces efficiency whereas a Switch is also called intelligent hub since
it redirects the received information/ packet to the intended node(s).

In a large network a switch is preferred to reduce the unwanted traffic in the network
which may also reduce the bandwidth and cause network congestion.
1 mark for each

OR
 WAN is also called as Wide Area Network. It is a network of computing devices
crossing the limits of city, country or continent. It covers area of over hundreds or
thousands of kilometres radius. For example: Network of ATMs, BANKs, National or
International organization offices spread over a country or continent.
MAN is also called as Metropolitan Area Network. It is a network of communicating
devices within a city. It covers an area of few kilometres to few hundreds kilometres.
For example: Network of schools, bank, and government offices within a city.
Best example of WAN is the Internet.
1 mark for each

26 Ans. 2
a. PHP-Hypertext Text markup Language
b. ITA-Information Technology Act
c. SIP- Session Initiation Protocol
d. GSP-Global system for mobile communication
½ mark for each.
27 When you assign a value to the parameter (such as param=value) and pass to the 2
function (like fn(param=value)), then it turns into a keyword argument.

Or
Ans. The program part(s) in which a particular piece of code or data value can be
accessed is known as variable scope. In python broadly scopes can either be global
scope or local scope.

28 def func(a): #def 2

s=m=n=0 #local variable
 for i in (0,a): #indentation and frange function missing
if i%2==0:
s=s+i
elif i%5==0: #elif and colon
m=m+i
else:
n=n+i
print(s,m,n) #indentation
func(15)
2 amrks for any four corrections.
29 (i) (ii) are correct answers. 2
30 Constraints are the checking condition which we apply on table to ensure the 2
correctness of data . example primary key, nut null, default, unique etc
1 mark for definition. 1 mark for 2 examples.
31 import mysql.connector as mydb 2
conn= mydb.connect(host=”localhost”, user=”root”, passwd=”1234”)
cur=conn.cursor()
cur.execute(“INSERT INTO student values(1,’AMIT’,22);”)
cur.commit()
½ mark for import
½ for connection
½ for execute
½ for commit
32 Primary key is an attribute or set of attributes that uniquely identify the values and can 2
appear as foreign key in another table..
Candidate key is an attribute or set of attributes that you can consider as a Primary key.
 1 mark for each.

33 200 # 100 2

200 # 200 1 mark for each line

34 def listchange(arr,n): 3

l=len(arr)
for a in range(l):
if(arr[a]%2==0):
arr[a]=10
else:
arr[a]=arr[a]*5

a=[10,20,23,45]
listchange(a)
print(a)
1 mark for function
1 mark for loop and condition checking
1 mark for if and else
35 f=open("C:\\xii_ip\\abc.txt","r") 3
linesList=f.readlines()
count=len(linesList)
print(count)
f.close()
1 mark for open() 1 mark for readlines() 1 mark for count and close
OR
file=open("C:\\xii_ip\\abc.txt","r")
c=0
line = file.read()
word = line.split()
 for w in word:
if w=='if':
print( w)
c=c+1
print(c)
file.close()
1 mark for open() 1 mark for read() and split() 1 mark for count and close

36 (i) 2 3
(ii)
Manufacturer Min max
LAK 40 40
ABC 45 55
XYZ 95 120

(iii)
ProductName ClientName
Face Wash Total Health
37 def PushEl(element): 3
a=int(input("enter package title : "))
element.append(a)
def PopEl(element):
if (element==[]):
print( "Stack empty")
else:
print ("Deleted element:", element.pop())
or

def InsertQ(queue):
a=input(“Enter customer name :”)
queue.append(a)
def DeleteQ(queue):
if (queue==[]):
print (“Queue is empty…..”)
else:
print(“Deleted element is”, queue[0])
del queue[0]
38 . B_Town 5
2. Star Topology
 Village -
Village -
3
2
B_Town
Village -
1

3. Hub/ Switch
4. Telnet
5. Firewall
39 a. Select R.RecIC, S.Sendername, S.SenderAddress, R.RecName, R.RecAddress from 5
Sender S, Recepient R where S.SenderID=R.SenderID ;
b. SELECT * from Recipent ORDER By RecName;
c. SELECT COUNT( *) from Recipient Group By RecCity;
d.Select * from sender where Sendercity=’mumbai’;
e. update recipient set RecName=’S Rathore’ where RecID=’ KO05’
1 mark for each correct answer.
40 import pickle 5
def CreateEmp():
f1=open("C:\\xii_ip\\emp.dat",'wb')
eid=input("Enter E. Id")
ename=input("Enter Name")
designation=input("Enter Designation")
salary=int(input("Enter Salary"))
l=[eid,ename,designation,salary]
pickle.dump(l,f1)
 f1.close()
import pickle
def display():
f2=open("C:\\xii_ip\\emp.dat","rb")
try:
while True:
rec=pickle.load(f2)
if rec[3]>5000:
print(rec[0],rec[1],rec[2],rec[3])
except:
f2.close()
display()
2 and ½ mark for each function
OR
(i)
import pickle
def createemp:
f1=open("emp.dat",'ab')
eid=input("Enter E. Id")
ename=input("Enter Name")
designation=input("Enter Designation")
salary=int(input("Enter Salary"))
l=[eid,ename,designation,salary]
pickle.dump(l,f1)
f1.close()
ii)
def display():
f2=open("emp.dat","rb")
try:
while True:
rec=pickle.load(f2)
if (rec[2]=='Manager'):
print(rec[0],rec[1],
rec[2],rec[3])
except:
break
f2.close()