Binary coded decimal (BCD) is a system of writing numerals that assigns a four-digit binary code to each digit 0 through 9 in a decimal (base-10) numeral. The four-bit BCD code for any particular single base-10 digit is its representation in binary notation, as follows:

0 = 0000
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
6 = 0110
7 = 0111
8 = 1000
9 = 1001

The major problem with BCD code is that only 64 (2 to the power 6) different character can be represented in it. And EBCDIC was obsolete by ASCII because EBCDIC did not use continuous coding (all the letters of the alphabet in increasing binary values), and because IBM made it difficult for others to use.