Standard file handles

          0       Standard input device           Stdin
          1       Standard output device          Stdout
          2       Standard error device           Stderr
          3       Standard auxiliary device       Stdaux
          4       Standard printer device         Stdprn


       Stdin          This is usually the keyboard, but it can be
                      redirected so that input is read from a file.

       Stdout         This is usually the display, but can be redirected
                      so the output is written to a file.

       Stderr         This is the display and cannot be redirected on the
                      command line.  Stderr is useful for displaying error
                      or copyright messages that you don't want
                      redirected.

       Stdaux         This is usually a serial device, and is the same as
                      the DOS `AUX:' device.  You can both read from and
                      write to this device.

       Stdprn         This is usually the printer, and is the same as the
                      DOS `PRN:' device.  You can both read from and write
                      to this device.

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    The file handles listed above are open when a program first starts.
    You don't need to explicitly open any of these devices unless you had
    previously closed one of these file handles.

       Notes:         All five predefined handles are in ASCII mode, which
                      means that DOS attaches special meaning to a number
                      of characters, including Ctrl-C (Ctrl-Break), Ctrl-
                      S, and Ctrl-P.  In ASCII mode, Ctrl-Z is treated as
                      an end-of-file mark; characters read from Stdin are
                      echoed to the screen; control characters written to
                      Stdout and Stderr are displayed as a x sequence
                      (for example, D); and tabs are filled with spaces
                      to the next 8-character boundary.

                      You can change the mode of these devices between
                      ASCII and binary using the IOCTL calls (DOS function
                      44h).  Note, however, that because the first three
                      devices (Stdin, Stdout, and Stderr) are all
                      duplicate handles, changing the mode on any one
                      changes the mode for the other two.