Which of the following binary codes for decimal digits are self complementing?

(a) 8421 code

(b) 2421 code

(c) excess-3 code

(d) excess-3 gray code

Choose the correct option :

1. A(a) and (b)
2. B(b) and (c)
3. C(c) and (d)
4. D(d) and (a)

Pick an option to check yourself, or open the answer below.

Show answer & explanation

Correct answer: B. (b) and (c)

Explanation

In 2421 and excess-3, the code for 9 − d is the bit complement of the code for d.