Have you ever met warning C4828?

warning C4828: The file contains a character starting at offset 0x308 that is illegal in the current source character set (codepage 65001).
warning C4828: The file contains a character starting at offset 0x31b that is illegal in the current source character set (codepage 65001).
warning C4828: The file contains a character starting at offset 0x6dd that is illegal in the current source character set (codepage 65001).

Remove all chararacters in your code as “áàâäãéèêëí,…” in comments too and your warning will vanish.

Or you can disable it with preprocessor by pasting this in your file causing troubles :

#pragma warning(disable:4828)

You’re quite right! Thank you very much! it was “illegal” characters in comments (copied from book).

Check out my answer under accepted answer over here.
There’s no need to remove those.