What is a binary coded decimal number?
A binary coded decimal number (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 standard consists of four bits that effectively represent the decimal values 0 to 9. This writing format system is used because the size of a number is not limited. Four bits can simply be added as another decimal digit from a true binary representation, which is limited to the common powers of two such as 16, 32 or 64 bits.
Binary coded decimal numbers are an easy way to represent decimal values as each digit is represented by its own 4-bit binary sequence that has only 10 different combinations. In comparison, converting a true binary representation to a decimal number requires arithmetic operations such as multiplication and addition.
Conversion to decimal digits for display or printing is easier, but the circuitry required to implement this system is more complex. For example, the binary coded decimal number means '1001 0101 0110', the three groups of 4 bits each have three decimal places. In left to right order, the resulting decimal value is 956.
The 4-bit binary representation of the decimal values follows:
0 = 0000
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
6 = 0110
7 = 0111
8 = 1000
9 = 1001