Page 73 - Computer Science V2.0 Class 11

Case-based Questions

1. Nirankar has just learnt about the hexadecimal number system. With his previous knowledge of the decimal number
system, he knows how to compute the value using the place value and face value of symbols given in the number. He has
computed the decimal value of the hexadecimal number system, (D20.B1) as given below:
16
(D20.B1) 16
-1
= D × 16 + 2 × 16 + 0 × 16 + B × 16 + 1 × 16 -2
0
1
2
= 13 × 1 + 2 × 16 + 0 × 256 + 11 × 0.0625 + 1 × 0.0039
= 13 + 32 + 0 + 0.6875 + 0.0039
= (45.6914)
2
Is the computation correct? If not, give the correct computation.
2. Sheikh just came to know that hexadecimal numbers are used to represent colors in digital form. He knows that red, green,
and blue are the three primary colors, referred to as RGB. He has formed a table that gives the name of the color along with
its decimal value and hexadecimal value. Help him complete the table.

Name of Colour Decimal Value Hexadecimal Value
Yellow (FF, FF, 00)
(256, 0, 0)
Blue (0, 0, 255)
Black
Green (00, FF, 00)

3. Saptarishi is learning about ASCII, which is a 7-bit encoding scheme to codify 128 different characters. He now wants to
encode the following words using ASCII and thereafter write their binary equivalent. Help him complete the task. You may
refer to ASCII table given in the chapter.

Word ASCII Code Binary equivalent
BOT 66 79 84
KEY 75 68 89
NUMber 1001110 1010101 1001101 1100010
1100101 1110010
Yes–NO

NCERT Exercise Solutions

1. Write base values of binary, octal and hexadecimal number system.
Ans.

NUMBER SYSTEM BASE VALUE
Binary number system 2
Octal number system 8
hexadecimal number system 16
2. Give full form of ASCII and ISCII.
Ans. The full form of ASCII is American Standard Code for Information Interchange.
The full form of ISCII is Indian Script Code for Information Interchange.
3. Try the following conversions.
i. (514) = (?)
8
10
ii. (220) = (?) 2
8
Number Systems and Encoding Schemes 59