Packed BCD: Packed BCD Numbers are stored in two digits to a byte, in 4 bit groups referred to as nibbles. ALU is capable of performing only binary addition and subtraction, butby adjusting the sum or difference the correct result in packed BCD format.
Unpacked BCD: Unpacked BCD Format: In Unpacked BCD, there is only one digit per byte and because of this, unpacked multiplication and division can be done. Binary operations act on single bytes and the results are adjusted. For Division, the adjustment is done before the binary division.