Question

Which about fetch decode execute cycle in CPU are correct? I. Program counter is incremented after each instruction is fetched so the CPU move to the next instruction. II. The Control Unit is responsible for fetching instruction and placing them in the instruction register. III. The ALU is responsible for decoding instruction and determining which operation to perform. IV. Register are used to permanently store operating system's files for fast access.

• A. III, IV
• B. II, III
• C. I, II, III
• D. I and II

Hint:

Remember: PC → Stores next instruction address, CU → Fetches and decodes instructions, ALU → Performs arithmetic and logic operations, Registers → Temporary high-speed storage.

Answer 1

The Correct Option is D

Concept: The Fetch-Decode-Execute cycle is the fundamental process through which a CPU executes instructions. The major components involved are:

• Program Counter (PC)

• Control Unit (CU)

• Instruction Register (IR)

• Arithmetic Logic Unit (ALU)

• Registers

Step 1: Examine Statement I.
The Program Counter stores the address of the next instruction to be executed. After an instruction is fetched, the Program Counter is normally incremented so that it points to the next instruction. Therefore Statement I is correct.

Step 2: Examine Statement II.
The Control Unit fetches instructions from memory and places them into the Instruction Register. Hence Statement II is also correct.

Step 3: Examine Statement III.
Instruction decoding is performed by the Control Unit, not by the ALU. The ALU performs arithmetic and logical operations after decoding. Therefore Statement III is incorrect.

Step 4: Examine Statement IV.
Registers are temporary high-speed storage locations inside the CPU. They do not permanently store operating system files. Permanent storage is done using secondary memory such as SSDs or HDDs. Therefore Statement IV is incorrect. Hence only Statements I and II are correct. \[ \boxed{\text{Answer (D)}} \]