>I have been watching this with great interest. (Flame suit on) Isn't it
>funny how we can miss the point and drift of into a tangent (Flame suit
>off), one has to ask the question of what the operating system is for, and
>is there any other way. Remembering that the requirement is to not use
>interrupts. If this is so then the programmer will have to spend much time
>counting instructions in order to control the task switching.

Not necessarily - the task switching could be based strictly on priority,
or round robin where a task runs to completion.

Probably not very common but there might be some applications.