Solved Board Paper For CBSE Class 12 Computer Science

(a) del a[5:9]

(b) [1,4,7]

(c) isalpha()

(d)

(i) 6

(ii) 0

(e) The code is printing 2 endlessly because the base case j > n is never reachable. The reason is that value of i becomes 1 for each call to function result().

def result(n):

The correct code will be:

if n==0 :

return

else:

result(n-1)

print(n)

(f)

(i) ‘rb’- In read only mode file must exist already, otherwise Python raises I/O error.

(ii) ‘ab’ – In append mode file is in write only mode. If the file exists, the data in the file is retained and new data.

(g) import matplotlib.pyplot as plt

res=[42.1,19.4,23,44,52]

locations=[‘East’, ‘West’, ‘North’, ‘South’, ‘Central’]

plt.axis(“equal”)

plt.pie(res,labels= locations, explode=[0,0,0.2,0,0], autopct= “%1.2f%%”)

plt.show()

(h) def copy(a1, a2):

fin=open(a1,"r")

fout=open(a2,"w")

while True :

text= fin.readline()

if len(text)==0:

break

if text[0]=="*":

continue

fout.write(text)

fin.close()

fout.close()

copy("content1.txt","content2.txt")

(i) def Recurgcd(a, b):

low = min(a, b)

high = max(a, b)

if low == 0:

return high

elif low == 1:

return 1

else:

return Recurgcd(low, high%low)

(a) NIC ontrols the wired and wireless connections of a computer to exchange information with other computers and the Internet.

(b) (i) Public clouds are the clouds used by multiple organization on a shared basis and managed by a third party service provider.
(ii) Community clouds are the clouds used by a group of related organisations who wish to make use of a common cloud computing environment.
(c) A switch is able to handle the data and knows the specific addresses to send the message. Router is actually a small computer that can be programmed to handle and route the network traffic.
(d)
i. Sensors
ii. RFID(Radio Frequencies Identification)
(e) i. Internet Message Access Protocol
ii. Secure Shell
(f) The sender, which is the checksum generator, follow these steps :

• The units are divided into k sections each of n bits.
• All sections are added together using 1’s complement to get the sum.
• The sum is complemented and become the checksum.
• The checksum is sent with the data.

(g) The following types of errors may occur:

• Single bit error- This type of error occurs if only one bit of the transmitted data got changed from 1 to 0 or from 0 to 1.
• Multiple-bit error- This type of error occurs if only two or more non consecutive bits in data got changed from 1 to 0 or from 0 to 1.
• Burst error- This type of error occurs if two or more consecutive bits in data got changed from 0 to 1 or from 1 to 0.

(a) Having clause is used to specify filtering conditions for groups.

(b) A table alias is a temporary label given along with the table name in FROM clause.

(c) The CHAR datatype specifies a fixed length character string. When a column is given data type as CHAR(n), then MYSQL ensures that all values stored in that column have this length of bytes.
VARCHAR specifies a variable length string. When a column is given datatype as VARCHAR(n), then the maximum size a value in this column can have is n bytes.

(d) The types of SQL functions are:
i. Single Row(Scalar) functions
ii. Multiple Row(Group/Aggregate) functions

(e) In an equi-join, the values in the columns being joined are compared for equality. All columns in the tables being joined are included in the results. Here, all columns from joining table appear in the output even if they are identical.
Non-equi-join is a query that specifies some relationship other than equality between the columns.
(f)
(i) SELECT COUNT(Item) FROM Infant WHERE Discount> 10 ;
(ii) SELECT Itemcode,UnitPrice FROM Infant ORDER BY Unitprice DESC ;
(iii) UPDATE Infant SET UnitPrice = UnitPrice + 0.1* UnitPrice ;
(iv) SELECT MAX(UnitPrice) FROM Infant ;
(v) SELECT Items FROM Infant WHERE Item LIKE %Baby% ;
(vi)

(vii) 1750

(a) E-waste or Electronic waste may be defined as discarded electrical or electronic device and electronics which are used for for refurbishment, reuse, resale, recycle or disposal.
(b) Digital/computer forensics

(c) (i) Sophisticated Virtual keyboard software
(ii) A joystick

(d) Identity threat can be protected by:
i. Using Unique Ids to protect our accounts and devices
ii. Using Bio-metric protection

(e) GPL-General Public license is commonly used for open source projects. It guarantees a good range of rights to developers who work on open source project.
LGPL- Lesser General Public license is used to license free software so that it can be incorporated into both free software and proprietary software.

(f) The gender issues in the field of computer science are:
i. Lack of interest among girls
ii. Lack of motivation for girls