Signed number representation — most common method Which signed-binary representation is most commonly used in digital systems for arithmetic?
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A2's-complement system.
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B1's-complement system.
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C10's-complement system.
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Dsign-magnitude system.
Answer
Correct Answer: 2's-complement system.
Explanation
Introduction / Context:Storing negative numbers in binary requires a signed representation. Hardware designers overwhelmingly choose one approach because it simplifies arithmetic and hardware implementation. This question asks you to identify that dominant choice.
Given Data / Assumptions:
- Target: general-purpose CPUs, microcontrollers, DSPs.
- Requirements: efficient addition/subtraction, unique zero, straightforward overflow behavior.
Concept / Approach:2's-complement provides a single representation for zero, simple subtraction by addition of complements, and the same adder hardware for signed and unsigned arithmetic. 1's-complement has two zeros; sign-magnitude complicates arithmetic with separate sign handling. 10's-complement is for decimal systems, not binary hardware.
Step-by-Step Solution:Compare properties: unique zero, simple adder reuse → 2's-complement excels.Note disadvantages in alternatives: two zeros in 1's-complement; sign-magnitude requires extra sign logic.Hence, the most common method is 2's-complement.
Verification / Alternative check:ISA specifications (e.g., x86, ARM, RISC-V) and compiler assumptions confirm 2's-complement as the de facto standard for signed integers.
Why Other Options Are Wrong:
- 1's-complement: dual zeros and end-around carry complexity.
- 10's-complement: decimal-specific, not binary hardware.
- Sign-magnitude: inefficient arithmetic and two sign cases.
Common Pitfalls:
- Confusing the 2's-complement operation with bitwise NOT (which is 1's-complement).
- Forgetting that range is asymmetric (one extra negative value) in 2's-complement.
Final Answer:2's-complement system.