UGC NET CSE | August 2016 | Part 2 | Question: 7

Question

Which of the following is the most efficient to perform arithmetic operations on the numbers ?

• A. Sign-magnitude
• B. $1's$ complement
• C. $2's$ complement
• D. $9's$ complement

Comments

$2's$ complement.

Answer 1

Answer will be C   2's complement

1. In 1's complement  there are TWO values of zero.A -0 (11111111) and a +0 (00000000),. On the other hand, in 2's complement, there is only one value for 0 (00000000). 

2. While doing arithmetic operations like addition or subtraction using 1's complement, we have to add an extra carry bit, i.e 1 to the result to get the correct answer. 2's complement has no such extra calculation

Answer 2

Sign's magnitude is only for sign convention (MSB is 1 then no is negative and if 0 then no is positive). Main difference is that while adding numbers using 1′ s complement, we first do binary addition, then add in an end-around carry value. But, 2′ s complement has only one value for zero, and doesn’t require carry values. 9’s complement of a decimal number is the subtraction of it’s each digits from 9. Like 1’s complement, 9’s complement is used to subtract a number using addition. 2's complement representation is unambiguous for 0 (i.e., only positive 0), but Sign-magnitude, 1’s complement and 9’s complement are ambiguous representation for 0 (i.e., both positive and negative 0). So, option (C) is correct.