Two's-complement calculation: Find the 2's-complement of 00001111 (8-bit representation).
Digital Electronics
Digital Arithmetic Operations and Circuits
Difficulty: Easy
Choose an option
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A11111111
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B11110000
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C11110001
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D11110111
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E00010000
Answer
Correct Answer: 11110001
Explanation
Introduction / Context:Two's-complement is the dominant signed number encoding in digital systems. It is formed by inverting all bits (one's-complement) and then adding 1 to the least significant bit.
Given Data / Assumptions:
- Original byte: 00001111 (decimal 15).
- We want its 2's-complement in 8 bits.
Concept / Approach:2's-complement(X) = (~X) + 1. For 00001111: one's-complement is 11110000; adding 1 yields 11110001.
Step-by-Step Solution:
Compute one's-complement: 00001111 → 11110000.Add 1: 11110000 + 00000001 = 11110001.Confirm bit width: keep 8 bits.Verification / Alternative check:Adding the number and its 2's-complement gives 00000000 with a carry out, confirming correctness.
Why Other Options Are Wrong:
11111111: That is 2's-complement of 00000001.11110000: Only one's-complement; missing +1.11110111: Incorrect increment.00010000: Not related to the required operation.Common Pitfalls:Stopping at inversion without adding 1, or changing bit width inadvertently.
Final Answer:11110001