... and a lot of different formats too. Each of those extensions stores data in a completely different way, with the possible exception of "wave" -- I'm not familiar with that one being used, but it might be similar to the way some HTML files use the ".htm" extension and others use ".html"... which is, I guess, another example of the same format using multiple extensions. But I think that was done just because HTML came before long filename support was introduced as a standard feature in the operating system.
