Is it just / ?
I kid. But really, besides “its all a file”, if you take away the gui, is the only difference the syntax ? How libraries interact? How disks are mounted ?
If we stripped all ms’s junk out and made windows open source, would we still prefer linux?
When you get to a very basic level, is one of them more efficiently coded?
The OS bundled with TI-84 Plus CE Python Edition graphing calculators is a wacky one. It runs primarily on an eZ80 core for backwards-compatibility with earlier graphing calculators while also handling an ARM core for Python functions. Parts of the assembly code can be traced back to the TI-82 calculator ROM from 1993.
Most people wouldn’t think a calculator would ever need a security solution, but it even verifies application signatures so students are less likely to load cheating utilities on them.
The HP 49g+/39g+ and their descendants the 50g/39gs run the same operating systems as the older 49g/39g except most of it runs in an emulator so they could replace the old Saturn CPUs with ARM ones. And it still runs way faster than the native version on the older devices somehow.
Plus the entire operating system is written in Reverse Polish Lisp, one of the strangest languages I’ve ever seen. Very strange devices, but still leagues ahead of any calculator produced since (at least the 49/50, the 39 is very confusing)
My TI-89 got me through college.