That is a "real difference" from "scheduling" "pre-emptive" etc.

What I tried to say, and I guess failed, was that many of these OS's (I used the word alleged) are just frameworks. Many of them are closer to what you and I use. I've seen lots of (interesting) published work over the years for variations of what you and I probably use, but unfortunately the author may have used the term RTOS or similar to draw attention to it. It's an obvious, albeit incorrect, acronym to use. Back to the point, these frameworks are sometimes little gems. Although I've fallen in the rut of being "productive" in recent years (translation: using the same framework), I probably should perhaps be working on variations, if for no other reason than to keep my brain from turning to rust.

Now, I'm not saying that there aren't people trying to wedge full-scale RTOS's into 8051's. I'm sure they are, but I hope they realize it's more an academic endeavour or a hobby rather than a practical one. Or else they take joy in using as much software a possible to get the job done.

For instance when I see a post about "function pointers on the '51" I cringe because it is the most inefficient thing you can think of on a '51.

Oh, oh. Well I haven't used one since 1998, and now that you mention it, maybe I should consider using them more often ;-)

This is how it looked and the code wasn't so big.

// Execute the current UI context.
(*focus)();

In 1989 it was used for a section of code the controlled a complex LCD menuing system (I'm sure there were over 100 "screens"). Every menu had it's own chunk of screen text code (that the user sees) and functions that were executed in response to the 4 or 5 buttons that the user had. It worked very well and there were no issues with code bloat because of it. It's really quite intuitive and compact once you see how it works. It would have been a hideous mess of switch statements/tables without it. "Focus", "context" and LCD menuing go very well hand-in-hand. I did this work prior to reading Niall Murphy's stuff in ESP mag, but it's in a very similar vein. Never say never.