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

Step 1: Name the players in the cycle.
The fetch-decode-execute cycle uses the Program Counter (PC), Control Unit (CU), Instruction Register (IR), Arithmetic Logic Unit (ALU) and general registers. Keeping each one's job straight settles every statement.
Step 2: Check Statement I (Program Counter).
The PC holds the address of the next instruction; right after a fetch it is incremented so the CPU advances. Statement I is correct.
Step 3: Check Statement II (Control Unit).
The CU is exactly what fetches an instruction from memory and drops it into the Instruction Register. Statement II is correct.
Step 4: Check Statement III (ALU decoding).
Decoding is the Control Unit's job, not the ALU's; the ALU only carries out arithmetic and logic once the instruction is decoded. Statement III is wrong.
Step 5: Check Statement IV (registers as permanent storage).
Registers are tiny, fast, temporary storage inside the CPU. Permanent files live on disks (SSD/HDD), so Statement IV is wrong.
Step 6: Collect the survivors.
Only Statements I and II hold up.
\[ \boxed{\text{I and II}} \]