Devices that do single character I/O could be attached to non seekable
host OS devices (tty, pipes, etc.) and thus shouldn't count on fseek()
and ftell(). These DEVICEs on these simulators do single character I/O
and easily can update their POS REGisters to reflect how much data has
been emitted. Changing such a REGister will have no useful effect
when attached to a non seekable file.
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