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:
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
Discussion & Comments