Which of the following flag is not affected by CMP instruction? A) Zero flag B) Carry flag C) Sign flag D) Parity flag

To determine which flag is not affected by the CMP (compare) instruction, we need to understand how the CMP instruction operates and what flags it typically modifies.

Breakdown of the CMP Instruction

1. CMP Instruction Function: The CMP instruction compares two operands by subtracting the second operand from the first operand but does not store the result. Instead, it sets or clears the flags based on the outcome of that subtraction.

Relevant Concepts

2. Flags Affected by CMP:
   • Zero Flag (ZF): Set if the result of the subtraction is zero (i.e., if both operands are equal).
   • Carry Flag (CF): Set if there is a borrow in the subtraction (i.e., if the first operand is less than the second operand).
   • Sign Flag (SF): Set based on the sign of the result (i.e., if the result is negative).
   • Parity Flag (PF): Indicates whether the number of 1 bits in the result is even or odd.

Analysis and Detail

3. Identification of Unaffected Flag:
   • The Zero, Carry, and Sign flags are all affected based on the condition of the operands compared.
   • The Parity flag may or may not change depending on the specific values being compared. It may not provide relevant information for normal arithmetic operations since CMP focuses on relative magnitudes rather than on bit parity.

Verify and Summarize

4. Conclusion: While all of the mentioned flags can be affected by the operations close to CMP, the Parity Flag (D) is generally less relevant in this context, as its indication reflects the number of 1-bits rather than the result of the comparison.

Final Answer

D) Parity flag