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CWD             Convert Word to Doubleword           Flags: Not altered

CWD

        Logic  if AX < 8000h
                  DX . 0
               else
                  DX . FFFFh
               endif

    CWD converts the signed word in AX to a signed doubleword in the
    DX:AX register pair by extending the most significant bit (the
    sign bit) in AX into all the bits of DX.

    Note
    The 32-bit form of CWD is CDQ.

    
    Opcode      Format
    99          CWD


    Length and timing
    Operands    Bytes   8088    186     286     386     486     Pentium
    -            1       5       4       2       2       3       2   NP