See Single-byte Character Set Support in The GNU
Emacs Manual. On a Unix, when Emacs runs on a text-only terminal
display or is invoked with ‘emacs -nw’, you typically need to use
set-terminal-coding-system to tell Emacs what the terminal can
display, even after setting the language environment; otherwise
non-ASCII characters will display as ‘?’. On other operating
systems, such as MS-DOS and MS-Windows, Emacs queries the OS about the
character set supported by the display, and sets up the required
terminal coding system automatically.