Well then, it's neither binary nor ASCII - it's a text file using some encoding which supports French characters. (True) ASCII does not. However most common European-language encodings are based on ASCII - they just add additional characters after 127, which are not part of ASCII.
To differentiate text from binary files (assuming there's no obvious difference in file extensions, you can do something much like Steve's suggestion - you just have to find out what encoding is actually used in the file. One common possibility is
Cp-1252 (Windows Latin-1). Look at the table of characters and identify a group of codes which are not possible in a valid text document on your system. (Usually 0x00-0x08, 0x0B, 0x0C, and 0x0E-0x1F is a good starting poin.) If any of these characters is present in a file, it's probably binary, not text. You'll want to
test carefully on many of your files to be more sure though. Good luck...
[ October 19, 2002: Message edited by: Jim Yingst ]