**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??

**EBCDIC**

—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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