What Does Binary-Coded Decimal (BCD) Mean?
A binary-coded decimal (BCD) is a type of binary representation for decimal values where each digit is represented by a fixed number of binary bits, usually between four and eight.
The norm is four bits, which effectively represent decimal values 0 to 9. This writing format system is used because there is no limit to the size of a number. Four bits can simply be added as another decimal digit, versus real binary representation, which is limited to the usual powers of two, such as 16, 32 or 64 bits.