Compute the 2's complement of the 16-bit binary word 0011 0101 1001 1100 and report the result as grouped bits.

Difficulty: Easy

Correct Answer: 1100 1010 0110 0100

Explanation:


Introduction / Context:
Two’s complement is the dominant representation for signed integers in computer systems. It enables straightforward addition/subtraction using the same binary adder hardware. Converting a positive binary word to its two’s complement negative (or vice versa) uses a simple invert-plus-one recipe.


Given Data / Assumptions:

  • Original 16-bit word: 0011 0101 1001 1100.
  • Spaces are visual groupings; they do not affect bit values.
  • We apply the standard 2’s complement operation.


Concept / Approach:

The two’s complement of a binary word W is computed by inverting every bit (forming the one’s complement) and then adding 1 to the result. This effectively computes 2^n − W for an n-bit word, which represents the arithmetic negation modulo 2^n.


Step-by-Step Solution:

1) Start: W = 0011 0101 1001 1100.2) One’s complement (invert each bit): 1100 1010 0110 0011.3) Add 1: 1100 1010 0110 0011 + 0000 0000 0000 0001 = 1100 1010 0110 0100.4) Result: 1100 1010 0110 0100.


Verification / Alternative check:

Hex cross-check: 0011 0101 1001 1100 = 0x359C; two’s complement = 0xCA64. Adding 0x359C + 0xCA64 = 0x10000 (overflow ignored in 16 bits), confirming correctness.


Why Other Options Are Wrong:

Options a, b, and d differ by one or more bits; none equals the computed sum after the +1 step. Therefore option c is the unique correct result.


Common Pitfalls:

Forgetting the +1 after inversion, mishandling carries across grouped spaces, or inverting only up to the first 1 from the right (which is an alternative shortcut but easy to misapply).


Final Answer:

1100 1010 0110 0100

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