Zero Flag

The Zero Flag (Z) is bit 1 of the Processor Status Register. The zero flag is set to 1 whenever an arithmetic, storage, or logical operation produces a result equal to zero, otherwise it is cleared to 0.

Examples

This example loads the accumulator with 0, then with 1, which sets the zero flag to 1 and then 0 respectively.

0001:A9 00     LDA #$00         ; Load A with $00. Since the result is zero, the Z flag is set to 1.
0002:A9 01     LDA #$0F         ; Load A with $0F. Since the result is not zero, the Z flag is cleared to 0.

Opcodes

The following opcodes affect the zero flag.

ADC AND ASL CMP CPX CPY DEX

DEY EOR INC INX INY LDA LDX

LDY LSR (Cleared) ORA PLP ROL ROR RTI

SBC TAX TAY TXA TYA