well, no all applications need to be updated constantly, in fact, some of it u can just leave it there and come back with the same session without doing anything. Even if apps runs at the same time, deep down, the processor can only handle one thread at a time. the way multiple programs are running in the same time is to have 1 thread per program and multiple thread sharing the CPU process time together, and since CPU can only handle 1 thread, apart from the thread it is processing, the rest of the threads are forced idle for a short period of time. That is how multiple task share a single processor.
So from how it works, you see that even running task are 'idle' for a very short time, maybe a few hundred clock cycles that we couldnt possible notice. Letting the program idle is not the same as quitting the program, as for idle mode, the program will still have all the sessions, whereby when you quit, it would be eliminated(whether saved or not).
Also, not all programs need to be be running at all time, for instance, facebook, twitter or email apps, we leave them running in the background right? So maybe every few minutes they will fetch updates/new mails from their respective server. Only when they need to update, their process is being called and run, other time, they are put into an idle state.
Extend from the previous scenario, let's say you are browsing a webpage and is using full ram now, the OS would just need to put the app's session into the virtual memory, and when the app is being invoke for updates, it just need to swap maybe part of the browsers info that is being stored at the ram, and run the process, after that, swap back. It's still multitasking because the apps are running at the same time, and it's automatically handled by the OS itself
Yes, with that should conclude the topic...
Different approach but all achieving the same thing. But there is still no NAND RAM.
However, I still dont believe we will find a truly fully multi tasking system.
Thanks for updating me on Iphone OS multi task approach.. I think its a pretty interesting system compared to a normal paging system.