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CBW             Convert Byte to Word                 Flags: Not altered

CBW

        Logic   if AL < 80h
                   AH . 0
                else
                   AH . FFh
                endif

    CBW converts the signed byte in the AL register to a signed word
    in AX by extending the most significant bit (the sign bit) of AL
    into all of the bits of AH.

    Note
    The 32-bit form of CBW is CWDE.


    Opcode      Format
    98          CBW


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