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Everything About BCD Code

I am always interested about Number and Coding System.As a devoted learner i always try to learn about coding system

Everything about BCD code


BCD code is one of the early computer codes.It is based on the idea of converting each digit of decimal number into its binary equivalent,rather than converting the entire decimal value into a pure binary form.This makes conversion process easier.

Where we can use BCD code?

We can use BCD coding system for electronic display board these days,BCD code was used in IBM super computer.

Number System

For understanding BCD Code properly we need to gain knowledge about positional number system first.

We mainly use 4 kinds of positional number system.They are





Decimal: Decimal number system is most commonly used number system it has 10 digits.And we also use it in our day to day life.As it has 10 digits in it.It's base is 10

Binary: This number system has only 2 digits. Only 0 and 1 is used here.So base is 2

Octal : It has 8 digits.So base is 8

Hexadecimal: This number system has 16 digits. So base is 16.But careful when when you reach digit 9 because after that there will be A=10,B= 11, C =12,D=13, E=14,F = 15 after that there will 10.Numeric data is not the only form of data, which is handled by a computer, we often require to process alphanumeric data also.An alphanumeric is a string of symbols,where a symbol may be one of the letters A,B,C,..... Z, or one the digit 0,1,2,.... 9 or a special character such as + - * /, . ()= ( space or blank) etc.An alphanumeric data consits of only letters A,B,C,........ Z and the blank character. Similarly numeric data consists of only numbers 0,1,2,....., 9.

For understanding properly follow I have made a chart for you

The chart is given below


How does it work?

Firstly, the full meaning of BCD code is binary coded decimal.The BCD equivalent of each decimal is shown below


All decimal digits are represented in BCD by 4 bits.

I am giving an example for making it easy.

42 is a decimal number. So its base is 10.

So 4210 is equal to 1010102 in a pure binary form.

But converting 42 into BCD produce different result and it is 01000010.

Important point to remember:

You have to convert each digit independently

And another thing you need to notice that only 16 configuration is possible here. Because 4 bits are used here ( 24=16).By the way from the chart that i have given only first 10 of these combination are used to represent decimal digits. The remaining 6 are not used.

So if i say 15 it means 00010101 in BCD

6 bit BCD Code

Many of you already noticed that 4 bit BCD Code system is insufficient for all representing all character used by computer

So 6 bit BCD code was introduced. And it is very useful cause it can represent 64 Character, for this 2 additional zone positions were added.Now this is sufficient for 10 decimal digits 26 alphabetic letters and 28 other special character.

Relationship Between Octal number system and 6 bit BCD Code

Since BCD is a 6-bit code, it can be easily divided into two 3 bit groups.Each of these 3-bit groups can be represented by 1 octal digit.so you can say that octal number system is used as shortcut notation for memory dump by computers,it uses BCD code for internal representation of characters.This result in a one-to -three reduction in the volume of memory dump.For better understanding i am giving an example. We are taking the word "BAD"

If we convert the word into BCD

Then the solution will be this.

B=110010 in BCD binary notation

A=110001 in BCD binary notation

D=110100 in BCD binary notation hence the binary digits 110010110001110100

Doing it using octal notation

B=62 in BCD octal notation

A=61 in BCD octal notation

D= 64 in BCD octal notation

So the BCD coding for the word "BAD " in octal notation will be 626164

For understanding the method properly i have added chart below follow it.


This all about BCD code.

If you have anymore question don’t hesitate to ask me

For understanding more accurately you can follow this video