An Arithmetic Logic Unit (ALU) is a multipurpose block capable of performing several logic and arithmetic operations, often selectable via control lines (opcodes). Evaluate this statement.

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
The ALU is central to processors and microcontrollers. It provides addition, subtraction, comparisons, bitwise logic, shifts/rotates, and sometimes multiplication support, controlled by instruction decode lines or micro-ops.


Given Data / Assumptions:

  • ALU takes operand inputs and control signals.
  • Outputs include result and flags (carry, zero, negative, overflow).
  • Target systems are general-purpose CPUs or embedded cores.


Concept / Approach:
By multiplexing internal function units (adder, logic unit, shifter), the ALU executes a range of arithmetic and logical operations. Control signals select the active function; results are typically registered and written back to architectural or microarchitectural registers.


Step-by-Step Solution:
1) Present operands A and B to ALU inputs.2) Control lines select operation: add, subtract, AND, OR, XOR, compare, shift, etc.3) ALU combines sub-block outputs and asserts flags.4) Result is forwarded to the register file or next pipeline stage.


Verification / Alternative check:
Block diagrams of classic and modern CPUs show multi-operation ALUs; instruction set manuals enumerate operations supported.


Why Other Options Are Wrong:
“Incorrect” is contrary to ALU definition. Claims that ALUs perform “only addition” or “only logic” ignore their combined arithmetic and logic capabilities.


Common Pitfalls:
Assuming ALU equals only adder; overlooking status flags and shift/rotate support common in ALU clusters.


Final Answer:
Correct

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