Having built software runnging on everything from microcontrollers to cloud servers to browsers, I also have no idea what an OS is.

In the context of a microcontroller, is it an RTOS? How is that different from something like Embassy with Rust, where hardware allocation and coordination is handled more at build time and less at runtime? In the context of a something showing up on a screen, is an OS something providing a UI framework and hardware abstraction - something like Win32 or Cocoa? What does that make Chrome?

In 2006 it felt like an answer to the question "what is an OS" was straightforward. In 2026, I'm rather confident that I don't have a single, simple answer. If there were ever a time to re-assess what we thought we knew about computing - now seems like a good time to do it.