`en_windows_xp_professional_with_service_pack_3_x86_cd_vl_x14-73974.iso` is also just raw numbers, but I believe Windows XP was copyrightable

Interesting.

From what I understand, copyright only applies to the original source code, GUI and bundled icon/sound/image files. Functionality etc. would fall under patent law. So the compiled code on your .ISO for example would not only be "just raw numbers" but uncopyrightable raw numbers.

Of course copyright applies to binaries too. It's long been established that compiled code is a derived work of its source.

A computer program is just 0s and 1s. Harry Potter books are just raw letters or raw numbers if an ebook.

(The combination is what makes it copyrightable).

In practice it's not the combination that is copyrighted (you cannot claim copyright over a binary just because you zipped it, or over a movie because you re-encoded it, for instance).

It's the “actual creativity” inside. And it is a fuzzy concept.