Question

On subtracting +28 from +29 using 2’s complement, we get ____________

(a) 11111010

(b) 111111001

(c) 100001

(d) 1

I had been asked this question in an interview.

My question is from 1’s, 2’s, 9’s & 10’s Complements in portion Number System and Codes of Digital Circuits

Answer 1

Right choice is (d) 1

To explain I would say: Steps For Subtraction using 2’s complement are:

-> 2’s complement of the subtrahend is determined and added to the minuend.

-> If the result has a carry, then it is dropped and the result is positive.

-> Else, if there is no carry, then 2’s complement of the result is found out and a ‘-’ sign preceeds the result.