As a general rule, filenames are listed in this "alphabetic" order in all Open and Save dialogs, as well as in shell window listings of files.

If you are using Unix, note that files whose names begin with lowercase characters [a-z] are listed after files with uppercase characters [A-Z]. Sooner or later, you'll forget to scroll down to the end of the list when looking for "foo.dx" when you don't see it listed between "Energy.dx" and "Gravity.dx".