:Not sure whether this is notable enough to be mentioned in the article, but you're right – versions later than 6 (2001) can open files created by all previous versions, but save files only in its own format, with a suffix of ".msX", where X is the version number (7, 8, 9, 10, 11, 12...). This is intentional, of course. Besides, all versions but 7 save files in a compressed format. ☭共产主义万岁★