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Definition

Character encoding is the process of assigning numeric code to a character set of different human languages across
the world, allowing them to be stored, computed, converted and transmitted using digital computers.

2.1 CHARACTERS AND THEIR ENCODINGS
A character set consists of a group of characters that are used to represent a particular language. The character set of
the English language is different from that of Hindi, Bengali, Chinese or any other languages spoken in different parts
of the world. The visual representation of a character is called a glyph. To represent these character sets, the computer
uses the concept of a coded character set, where each character is assigned a unique number called code points. The
code points are commonly referred to in decimal notation, though hexadecimal notation can also be used. Character
encoding demonstrates the way each code point is actually mapped with the glyph for that character. The evolution of
character encoding is discussed in the next sub-sections.

2.1.1 Binary Coded Decimal (BCD)
BCD is one of the oldest coding systems, where each decimal digit is expressed as a group of 4 bits or a nibble. These
4-bit binary numbers have their weights assigned as 8, 4, 2 and 1, from MSB to LSB. The BCD equivalent of decimal
digits from 0 to 9 is represented in the following table:

Decimal digit BCD equivalent
0 0000

1 0001
2 0010
3 0011

4 0100
5 0101
6 0110
7 0111

8 1000
9 1001

To represent the BCD of multi-digit numbers, we have to convert each digit to its BCD equivalent. For example, the
decimal number 10 has two digits 0 and 1. BCD of 0 is 0000 and 1 is 0001. So, 10 when converted to BCD will be
00010000.
Example 1: Write the BCD representation of 255.

Answer:

2 5 5
0010 0101 0101
So, the BCD equivalent of 255 is 001001010101.

The reverse conversion, i.e., BCD to decimal is similar. We have to make a group of 4 bits starting from the rightmost
bit and write the corresponding decimal equivalent from the above table.

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