The key feature of the excess-3 code is that it is self-complementing code. It means that 1’s complement of the coded number yields 9’s complementing of the number itself. The self-complementing property makes the ecess-3 code useful in some arithmetic operations, because subtraction can be performed using 9’ complement method and 1’s complement can be easily produced with digital logic circuits by simply inverting each bit.   _{Your Comment}