8085/ALU flags: “Z (Zero) flag is reset if an ALU operation results in 0.” Determine whether the statement is correct.

Introduction / Context:
Processor status flags reflect the outcome of arithmetic/logic operations. The Zero (Z) flag indicates whether the result of an operation is numerically zero. Misinterpreting set/reset polarity leads to incorrect branching and condition checks in assembly programs.

Given Data / Assumptions:

• 8085 (and many CPUs) define Z = 1 (set) when the result equals zero.
• Z = 0 (reset) when the result is non-zero.
• Applies across arithmetic and logical ALU operations that update flags.

Concept / Approach:

The statement claims the opposite of the specification. Correct behavior: if the result is 0, the Zero flag is set; if the result is not 0, the Zero flag is reset. This allows instructions like JZ/JNZ (jump if zero / not zero) to test equality efficiently.

Step-by-Step Solution:

Verification / Alternative check:

Consult 8085 instruction set summaries: after ANA, ORA, XRA, ADD/SUB etc., the Zero flag is set when the result equals 00h, and cleared otherwise.

Why Other Options Are Wrong:

• True / conditional variants: contradict standard 8085 flag definitions.
• Depends on carry: Zero flag is independent of carry; they are separate bits.

Common Pitfalls:

Reversing the meaning of “set” and “reset”; assuming only arithmetic updates Zero—logical ops also update it.

Final Answer:

False