Question

Which of the following statements about Arithmetic Logic Unit (ALU) is correct?

• A. ALU stores instructions permanently.
• B. ALU performs arithmetic and logical operations on data.
• C. ALU controls the execution of programs.
• D. ALU is responsible for input and output operations.

Hint:

Remember that the ALU is a purely combinational circuit. It does not have any memory of its own; it simply processes the inputs it receives from registers and sends the output back.

Answer 1

The Correct Option is B

Concept: The Central Processing Unit (CPU) is generally divided into three main components: the Arithmetic Logic Unit (ALU), the Control Unit (CU), and Registers.
• ALU: The "calculator" of the computer.
• Control Unit: The "manager" that directs traffic and flow.
• Registers: Small, high-speed storage for immediate data use.

Step 1: Defining the role of the ALU.
The primary function of the ALU is to perform mathematical calculations and logic-based comparisons. This includes addition, subtraction, multiplication, division, and logic operations like AND, OR, and NOT.

Step 2: Eliminating incorrect statements.

• (A) incorrect: Permanent storage is handled by secondary memory (HDD/SSD), and instructions are temporarily stored in the Instruction Register, not the ALU.
• (C) incorrect: Controlling execution is the job of the Control Unit (CU).
• (D) incorrect: I/O operations are handled by the I/O Interface or Input/Output Processor.

Step 3: Confirming the correct option.
Statement (B) directly describes the fundamental purpose of the ALU, making it the only correct choice.