# Computer Fundamentals Questions and Answers – Complements

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This set of Computer Fundamentals Multiple Choice Questions & Answers (MCQs) focuses on “Complements”.

1. What is the 1’s complement of 11010?
a) 11010
b) 11011
c) 00110
d) 00101

Explanation: The 1’s complement of a number is obtained by converting all the 0 bits to 1 and all 1’s to 0’s. Here, 11010 gets converted to 00101.

2. 2’s complement is obtained by adding 1 to 1’s complement of a number.
a) True
b) False

Explanation: The statement is true. Let us take an example: Consider the number 110000.
1’s complement of the number is 001111. 2’s complement=001111+1=010000.

3. The 10’s complement of 562 is __________
a) 436
b) 437
c) 512
d) 448

Explanation: 10’s complement is obtained by adding 1 to the 9’s complement of a number.
Here, 9’s complement=999-562=436.
Therefore, 10’s complement=436+1=437.
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4. The 9’s complement of 6578 is ___________
a) 1234
b) 3421
c) 3124
d) 3420

Explanation: 9’s complement is obtained by subtracting 9 from each bit of the number.
Here, 9999-6578=3421.
Therefore, the 9’s complement is 3421.

5. >> operator is used to denote _________
a) left shift
b) right shift
c) greater than
d) less than

Explanation: >> operator denotes the right shift in binary arithmetic.
E.g. If we say, >>110 by 2-bits, the value obtained will be 001.
Similarly, << denotes the left shift operator.
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6. The subtraction using 1’s complement of 110 – 100 will give the result ___________
a) -011
b) 011
c) 010
d) -010

Explanation: To subtract using 1’s complement: Take the 1’s complement of the 2nd number (here, 011) and add it to the first number. (110+011=1,001).
If the carry is generated, it is added to the result (001+1=010).
If a carry is not generated then it is converted to its 1’s complement form.

7. The result obtained on subtraction using 2’s complement of 1111-0010 will be _________
a) 11101
b) 11011
c) 1101
d) 1011

Explanation: Firstly, the 2’s complement of the 2nd number is obtained.
Then, if carry is generated, it is discarded and the number is positive.
Otherwise, 2’s complement of the result is obtained and the answer is negative.
Here, 1111+1110=1, 1101. Since carry is generated, it is discarded and the answer is positive.

8. The 1’s complement of 1111111110.101 is _______________
a) 1.010
b) 0000000000.010
c) 1111111110.101
d) 1.101

Explanation: The 1’s complement of a number is obtained by reversing the bits with value 1 to 0 and the bits with value 0 to 1. Here, 11111111110.101 gets converted to 000000001.010 in its 1’s complement format.

9. 7’s complement of 432 is _________________
a) 432
b) 543
c) 345
d) 777

Explanation: To find the 7’s complement of any number, we simply subtract 7 from each of the bits.
Here, 777-432=345. So, the 7’s complement is 345.

10. The 16’s complement of 74E will be __________
a) 8B2
b) F8B2
c) 2B8
d) 8C2

Explanation: The 16’s complement is obtained by finding 15’s complement of the number (i.e. subtracting each bit of the number by 15) and then adding 1 to it.
Here, 15’s complement of 74E is 8B1.
Therefore, it’s 16’s complement will be:
8B1 + 001 = 8B2.

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