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2.3.1 BCD (Binary Coded Decimal)
                 BCD is the oldest coding system where each decimal digit is expressed as a group of 4 bits or nibbles. These 4-bit binary
                 numbers have their weights attached as 8, 4, 2, and 1 from MSB to LSB. The BCD equivalent of decimal digits from 0 to
                 9 are 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.

                                                    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.
                 Example 2: Write the decimal representation of 1001100001100011.

                 Grouping in 4 bits and writing the decimal equivalent of each group:

                                          1001             1000            0110            0011
                                            9               8               6                3
                 So, the equivalent decimal number is 9863.

                 Application of BCD:
                 •  BCD systems are used in electronic counters, digital clocks, and pocket calculators.
                 Limitations of BCD:

                 •  BCD codes are inefficient as compared to binary codes. For example, 12 in binary is 1100 but in BCD notation it is
                   written as 0001 0010.
                 •  Arithmetic operations become more complex as compared to binary notation.
                 •  As BCD is a 4-bit code, it can only represent numbers and is incapable of handling non-numeric characters.
                 To represent alphabets in BCD, a 6-bit coding system was developed which could represent numbers, letters and
                 some special characters. It contains 2 zone bits and 4 numeric bits and can be represented using Octal equivalents.



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