[notacoward]

Some of these map to classes you might have taken in college - compilers, databases, AI, etc. I'd divide operating systems into more than one part:

* Core kernel (schedulers, memory management, virtualization) * Drivers * Filesystems * Networking

Then there are some specialties that cut across more than one of these - high performance computing, financial tech (not even counting blockchain stuff), security engineering, performance engineering. Then there's a whole world of embedded stuff, from teeny-tiny microcontrollers up to high-performance medical imaging or genomics, plus large distributed systems to control things like military equipment or nuclear power plants.

Really, there are so many different kinds of computing that we just never even hear of on a site like this. It's really the web/app/mobile front-end stuff that's a niche technology-wise. (On my less charitable days I'd call it a ghetto.) It's a hugely profitable niche, to be sure, but to me it still seems to get a disproportionate share of attention and funding compared to other stuff that's just as hard, just as fun, and just as important.