Not only the physical substrate, but the platform it runs on. Even 30 years (not much for a library/archivist) old software can bring substantial challenges.

Not only the physical substrate, but the platform it runs on. Even 30 years (not much for a library/archivist) old software can bring substantial challenges. Much more so if it was a closed system like a game console, or DRM protected binary that may or may not work in an emulator (if said emulator exists). I do wish that published software had a maximum license life, much like patents that would allow archiving.