CMP Arithmetic Comparison

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:

        CMP r8,r8
        CMP m8,r8
        CMP r8,m8
        CMP r16,r16
        CMP m16,r16
        CMP r16,16
        CMP r32,r32    386+
        CMP m32,r32    386+
        CMP r32,m32    386+
        CMP r8,i8
        CMP m8,i8
        CMP r16,i16
        CMP m16,i16
        CMP r32,i32    386+
        CMP m32,i32    386+
        CMP r16,i8
        CMP m16,i8
        CMP r32,i8     386+
        CMP m32,i8     386+
        CMP AL,i8
        CMP AX,i16
        CMP EAX,i32    386+

Examples:

        CMP BX,DI
        CMP EAX,5
        CMP AX,0FFFFH            ;Uses single-byte opcode
        CMP AL,42H               ;Uses single-byte opcode
        CMP BP,17H
        CMP WORD [BX+SI+Inset],5
        CMP WORD ES:[BX],0B800H

Notes:

CMP compares its two operations, and sets the flags to indicate the results of the comparison. The destination operand is not affected. The operation itself is identical to subtraction of the source from the destination without borrow (SUB), save that the result does not replace the destination. Typically, CMP is followed by one of the conditional jump instructions; that is, JE to jump if the operands were equal; JNE if they were unequal; and so forth.

        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