IT Topic4

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Wednesday, 12 February 2020

In the Early Days And BCD(binary coded decimal)

In the Early Days 

When computers were first introduced they were simply used for performing calculations
After a while scientists realized that computers can also be used to store and edit text in different ways

The problem was that a computer could only understand binary (1s & 0s)

BCD(binary coded decimal)

Very early memory codes.
Each decimal number converted to binary equivalent individually.
For example 39=0011 1001
Each decimal digit is converted individually to four bit binary
4 bits=>16 different characters.
Only sufficient to represent 10 numbers.
6 combinations are redundant.

6 bit BCD

To represent other characters on keyboard 6 bit BCD is used.
6 bits=> 64 different characters.
Sufficient for 26 alphabet+28 special characters+ 10 digits.
Can only present small letters.
What about capital??


64 different BCD codes are not sufficient for all the English letters upper and lower.
So Extended Binary coded decimal information interchange is used.
Its 8 bit code=>256 different symbols.

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