BCD

BCD is a system for storing decimal numbers in a binary form. Each digit of the decimal number is converted to a 4 bit binary number:

Decimal 0 1 2 3 4 5 6 7 8 9

BCD 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001

All numbers in decimal can be represented in BCD with the four bits easily able to represent numbers from 0 to 9.

For example: To represent the decimal number 312 in BCD form:

Decimal	3	1	2
BCD	0011	0001	0010

Note: Each digit of the decimal number (3,1,2) is separately converted to a binary number instead of converting the number 312 as a whole to the binary number 100111000.
You can see that the pure binary number takes up 9 bits while the three BCD numbers take up 12 bits, requiring more computer memory space.