Compute the two’s complement of the binary number 110110₂. Choose the correct 6-bit result.

Difficulty: Easy

Correct Answer: 001010₂

Explanation:


Introduction / Context:
Two’s complement is obtained by inverting all bits (one’s complement) and then adding 1. This operation is central to implementing subtraction using a binary adder and to representing negative integers in hardware.


Given Data / Assumptions:

  • Original number: 110110₂ (6 bits).
  • We want the 6-bit two’s complement.
  • No overflow beyond 6 bits is retained.


Concept / Approach:
The algorithm is: two’s complement(x) = invert_bits(x) + 1 (within the same bit width). The invert operation flips each 1 to 0 and each 0 to 1. The final addition is performed modulo 2^n, where n is the word size (here n = 6).


Step-by-Step Solution:

Start with x = 1 1 0 1 1 0.One’s complement: invert bits → 0 0 1 0 0 1.Add 1: 001001 + 000001 = 001010.Therefore, two’s complement(110110₂) = 001010₂.


Verification / Alternative check:
Check by addition: 110110₂ + 001010₂ = 1000000₂ (a 7-bit result). Discarding the carry beyond 6 bits yields 000000₂, confirming they are complements within 6 bits.


Why Other Options Are Wrong:
110100₂ and 101010₂ are not obtained by invert-plus-one. 001011₂ is off by 1 from the correct complement (it is the one’s complement plus 0).


Common Pitfalls:
Forgetting the final +1 after inversion, or accidentally extending the width during addition.


Final Answer:
001010₂

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