/* $DOC$
   $NAME$
      ft_inp()
   $CATEGORY$
      DOS/BIOS
   $ONELINER$
      Retrieve a byte from a specified I/O port
   $SYNTAX$
      ft_inp( <nPort> ) -> nValue
   $ARGUMENTS$
      <nPort> is the port from which to retrieve the byte.  If it is
      invalid in any way, the function will return zero.
   $RETURNS$
      The byte retrieved.
   $DESCRIPTION$
      It may sometimes be useful to read a byte from a port without having
      to resort to C or assembler.  This function allows you to do so.

      The source code is written to adhere to Turbo Assembler's IDEAL mode.
      To use another assembler, you will need to rearrange the PROC and
      SEGMENT directives, and also the ENDP and ENDS directives (a very
      minor task).
   $EXAMPLES$
      ? ft_inp( 100 )   // read a byte from port 100 (064h)
   $SEEALSO$
      ft_outp()
   $END$
 */