STD Set Direction Flag (DF)

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
          *                IF: Interrupt flag ZF: Zero flag CF: Carry flag

Legal forms:

        STD <none>

Examples:

STD

Notes:

STD simply asserts the Direction flag (DF) to the set (1) state. This affects the adjustment performed by repeated string instructions such as STOS, SCAS, and MOVS. Typically, when DF = 0, the destination pointer is increased, and decreased when DF = 1. DF is set to 0 with the CLD instruction.

        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