Variable: enable-multibyte-characters

Non-nil means the buffer contents are regarded as multi-byte characters.
Otherwise they are regarded as unibyte. This affects the display,
file I/O and the behavior of various editing commands.

This variable is buffer-local but you cannot set it directly;
use the function `set-buffer-multibyte' to change a buffer's representation.
See also Info node `(elisp)Text Representations'.