POP Pop Top of Stack into Operand

Flags affected:

        O D I T S Z A P C  OF: Overflow flag  TF: Trap flag AF: Aux carry
        F F F F F F F F F  DF: Direction flag SF: Sign flag PF: Parity flag
            <none>         IF: Interrupt flag ZF: Zero flag CF: Carry flag

Legal forms:

        POP r16
        POP m16
        POP r32
        POP m32
        POP sr

Examples:

        POP WORD [BX]
        POP EAX
        POP DX
        POP DWORD [EAX+ECX]
        POP ES

Notes:

It is impossible to pop an 8-bit item from the stack. Also remember that the top of the stack is defined (in 16-bit modes) as the word at address SS:SP, and there's no way to override that using prefixes. In 32-bit modes, the top of the stack is the DWORD at [ESP]. There is a separate pair of instructions, PUSHF and POPF, for pushing and popping the Flags register.

All register forms have single-byte opcodes. NASM recognizes them and generates them automatically, even though there are larger forms in the CPU instruction decoding logic.

        r8 = AL AH BL BH CL CH DL DH        r16 = AX BX CX DX BP SP SI DI
        sr = CS DS SS ES FS GS              r32 = EAX EBX ECX EDX EBP ESP ESI EDI
        m8 = 8-bit memory data              m16 = 16-bit memory data
        m32 = 32-bit memory data            i8 = 8-bit immediate data
        i16 = 16-bit immediate data         i32 = 32-bit immediate data
        d8 = 8-bit signed displacement      d16 = 16-bit signed displacement
        d32 = 32-bit unsigned displacement