Function 0Ch            Flush Buffer, Read Keyboard

    Removes any characters in the standard input buffer, then invokes
    the specified function.

        Entry   AH = 0Ch
                AL = Function to be invoked (06h, 07h, 08h)
                     (0Ah may not be used, 01h may be used but is
                      superseded)

        Return  AL = Return value from function
                     (zero if invalid function)

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    This function clears the keyboard buffer, then invokes a DOS
    service (specified in AL). The purpose is to ensure that your
    program receives new input before it performs the followup
    function.


    Note
    If used to call function 06h, this function must pass 0FFh in the
    DL register; it cannot be used to write a character.