/* $DOC$
   $NAME$
      ft_IsPrint()
   $CATEGORY$
      DOS/BIOS
   $ONELINER$
      Check printer status
   $SYNTAX$
      ft_IsPrint( [ <cDevice> ] ) -> lResult
   $ARGUMENTS$
      <cDevice> is optional and is the device to test (LPT2, COM1, etc.).
      If omitted, the function will default to the PRN device.
   $RETURNS$
      .T.  if device is ready for output.
      .F.  if one of the following conditions occurs:
           1)  The device is not ready.
           2)  The device does not exist.
           3)  DOS couldn't open the device for some reason
               (such as no file handles available).
   $DESCRIPTION$
      The Clipper IsPrinter() function is somewhat limited because it only
      works with LPT1.  Furthermore, it talks directly to the hardware, so
      if you have redirected LPT1 via the DOS MODE command, the IsPrinter()
      function will return erroneous results.

      This function offers a better alternative.  Instead of talking to the
      hardware, it issues a DOS call that checks to see if the device is
      ready or not.  That gives DOS an opportunity to deal with any
      redirections, and since you pass the device name as a parameter, you
      can test any device, not just LPT1 (note that the function defaults
      to PRN if you fail to pass a valid parameter).

      The function also temporarily traps the DOS critical error handler so
      you don't get any nasty error messages if the device isn't ready.  It
      restores the old critical error handler before exiting.

      Note that although this function is mainly designed for testing
      printers, you can also check to see if a drive is ready.  Since DOS
      thinks the NUL device exists on every drive, you can pass a drive
      letter followed by NUL as a parameter.  If DOS is able to open the
      NUL device, then the drive is ready, otherwise the door is open or
      something else is wrong.

      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).
   $EXAMPLES$
      IF ! ft_IsPrint()
         ? "PRN is not ready!"
      ENDIF

      IF ! ft_IsPrint( "COM2" )
         ? "Check the device on COM2.  Something is wrong."
      ENDIF

      IF ! ft_IsPrint( "/dev/lp0" )
         ? "Oops, not available."
      ENDIF
   $END$
 */