The instruction to "exclude non-ASCII characters" isn't particularly helpful.
The ASCII character set includes a lot of characters that a lot of file systems can't handle properly in filenames, e.g. ?, *, !, /, \, etc.
If you make sure your file name contains only western alphabet letters (either case) - a, B, c, etc. - arabic numerals - 1, 2, 3, etc. - hyphens and underscores (including the single "dot" before the file extension of course) then you shouldn't have any filename-specific problems.
This also means that you should avoid using spaces in filenames. Spaces can cause all kinds of problems when you move files between different file systems. (You get lots of %20% "garbage" in your file name.) Best to avoid them.