Hmmm. I created a system I called Sub-Machines back in the 80's too, though it never occurred to me that anyone else might be interested in it. I was particular

Hmmm. I created a system I called Sub-Machines back in the 80's too, though it never occurred to me that anyone else might be interested in it. I was particularly focussed on data communications protocol state machines. I could launch and detach, launch and camp (block), and launch and continue with other business until notified of a submachine's completion. Such notifications could also wake up camped super-machines. I could also get progress notifications bubbling back up. Worked a treat. To make it work I also had to create a co-operative function based multi tasking scheduler. It was very fast, and I still use it to this day. Part of the speed is not having to save context on every task switch. Takes planning though, unlike the lazy while(true) thread loops invented for junior programmers and used today way too much. But no real hardship when dealing with event driven systems, where each event has usually pretty short computations. Much easier to get true Hard Real Time systems to meet their targets.