Looking at that latest mental model, it's.. a bit suspicious that every program ends up calling the same set of functions. It's almost like something different happens when calling those.

Are those even regular functions? Can we step through them with a debugger?

If we run our stdio-powered C program in gdb, and break on read, we can confirm that we indeed end up calling a function (which is called here, but oh well):

Everybody knows how to use files. You just open up File Explorer, the Finder, or a File Manager, and bam - it's chock-full of files. There's folders and files as far as the eye can see. It's a genuine filapalooza. I have never once heard someone complain there were not enough files on their computer.

But what is a file, really? And what does reading a file entail, exactly?