Page 66 - ComputerScience_Class_11

Disadvantages of the ISCII code are as follows:
• A special keyboard containing ISCII character keys is required.
• After the development of the Unicode scheme which includes the ISCII codes, the latter became obsolete.
6. Define the following terms used in computer memory:
a. Bit b. Nibble
c. Byte d. Word
Ans. a. Bit: A bit is the smallest unit of data in a computer. It can store only one of two values 0 or 1.
b. Nibble: A nibble is a group of 4 bits. It is equal to half a byte.
c. Byte: A byte is made up of 8 bits. It is commonly used to represent a single character, such as a letter, digit or symbol.
d. Word: A word is a unit of data that the processor can store and process at one time. The size of a word depends on the
computer architecture. For example, in IBM architecture a word is 32 bits or 4 bytes, while in Intel PC architecture a word is
16 bits or 2 bytes.
7. Describe the BCD coding system and its applications.
Ans. BCD stands for Binary Coded Decimal. It is one of the oldest coding systems used to represent decimal numbers in binary form.
In BCD, each decimal digit is represented separately using a group of 4 bits called a nibble. The 4-bit binary number has weights
8, 4, 2 and 1 from the most significant bit to the least significant bit. For example, the decimal digit 5 is represented as 0101
in BCD.
Applications of BCD: BCD systems are used in electronic counters, digital clocks and pocket calculators where numeric display
is required.
8. State the different Unicode encoding schemes and explain each of them.
Ans. There are different Unicode encoding schemes namely UTF-8, UTF-16 and UTF-32:
• UTF-8: It is a multi-byte and variable width encoding scheme. It uses 1 byte for standard English letters, 2 bytes for additional
Latin and Middle Eastern characters, 3 bytes for Asian characters and 4 bytes for additional characters. This encoding scheme
is compatible with HTML, XML, JSON and e-mail.
• UTF-16: It uses 2 bytes to represent 65536 characters and 4 bytes for additional characters. It is used in operating systems such
as Microsoft Windows.
• UTF-32: It represents each character using 4 bytes.

D. Higher Order Thinking Skills (HOTS)
1. Elaborate on the need for extended ASCII and how it differs from original ASCII.
Ans. The original ASCII encoding system, introduced in 1960, was limited to 7 bits, allowing it to represent only 128 characters. These
included the English alphabet, digits and a limited set of special characters. However, as computing spread globally, it became
clear that there was a need to represent characters beyond English, especially for European languages that used additional
symbols, accented letters and characters.
To address this, extended ASCII was introduced, using 8 bits to represent 256 characters. This expansion allowed for the inclusion
of characters for languages like French, German and Spanish, along with graphic symbols and punctuation marks. While it
supported a wider range of characters, extended ASCII still had limitations, particularly in supporting non-Latin scripts, leading to
the development of more comprehensive systems like Unicode.
2. Critically analyse the role of UTF-8 encoding in modern computing. How does UTF-8 balance the need for space efficiency with
the need to represent diverse characters and why is it considered the most popular encoding scheme?
Ans. UTF-8 is a variable-length encoding that efficiently balances space usage and the representation of diverse characters. It uses 1
byte for standard English characters, 2 bytes for additional Latin characters, 3 bytes for characters from Asian languages and up to
4 bytes for even more complex symbols. This flexibility allows UTF-8 to be space-efficient while still accommodating a vast range
of global characters, making it suitable for modern computing needs, especially in web and internet-based technologies. UTF-8’s
backward compatibility with ASCII ensures that it can handle older data while supporting a broader character set. Its widespread
adoption is due to this versatility and its compatibility with most modern software and platforms.

E. Assertion and reasoning questions.
The following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appro-
priate option given below:
a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true but R is not the correct explanation of A.
c. A is true but R is false.
d. A is false but R is true.

64 Touchpad Computer Science (Ver. 3.0)-XI