If your file contains a code higher than 127 then it is not
ASCII -- ASCII stops at 127.
For example, it might be ISO 8859-1 (the code that Microsoft
refer to as "ANSI"). Many XML parsers will accept a file
containing characters from 8859-1 if you use an encoding
declaration at the start of the file:
<?xml encoding='ISO-8859-1'?>
However, the only encodings that XML parsers are obliged to
accept are the UTF-8 and UTF-16 encodings of ISO 10646
(informally, Unicode).
Mike Kay