Thanks Chris. That's very helpful.

I was also wondering about public memory variables. I've been doing some experimenting here (starting a thread, then starting another while having the first one sleep), and it looks like the memory pool allocated for public memory variables is also scoped to the thread, so each thread has its own (somewhat useless) pool of public memory variables.

What is the preferred way to set a global state indicator among all running threads that represent an instance of the same MTDLL COM object? I was hoping you could use public memory variables to hold state and employ the critical section SYS() for synchronization, but clearly that won't work.