I actually remember that I read that story and wondered in my head about the extension length. But I had two possible ideas what could make the story work. One

I actually remember that I read that story and wondered in my head about the extension length. But I had two possible ideas what could make the story work. One was that maybe they just hadn't used MS-DOS. There were plenty of computer systems out there and I had no knowledge what they used for programming the original MI or even which one was the original (it was available on different plattforms). The second was that maybe the extension was something like .brs as an abbrevation for brush, but they pronounced it brush and eventually took the pronounciation as the name, not the literal filename. Now I know both are wrong.