Reboot does not close apps?

[NYHorsewoman]

I "rebooted" my iPad this morning because last evening I sent emails and it doesn't seem like any of them went through, they weren't in drafts and they weren't in send, just gone. So I rebooted and it took a while with the swirly thing. Finally I restarted it and all the apps were still open when I double clicked the home button. Shouldn't a reboot close out everything and start fresh?

 

[Tim SPRACKLEN]

No - a reboot doesn't close the apps. It's because many of those apps are not really running, even though they appear in the multi-task bar. iOS removes most of them from RAM (system memory) and only a very few of the app's functions are left running - playing audio for example. The remaining apps that 'appear' to be running simply have their state ('context') stored so that the app can be reloaded in exactly the same state as when it was suspended. Those context files are not cleared by a reboot, so the apps still appear in the multi-task bar. The only way to delete the context file - and hence remove its app from the multi-task bar is to manually close the app by pressing an icon in the multi-task bar until they all start to jiggle and then pressing the upper left hand corner of the app's icon. That tells iOS to delete the app's context file and so it no longer appears in the multi-task bar......

Tim

 

[sjleworthy]

Look, he posted twice! Wot a nube

 

[Tim SPRACKLEN]

Damn - it's that 'Post Quick Reply' on a marginal 3G link in the ASDA car park...

Tim

 

[sjleworthy]

Yes, of course

 

[NYHorsewoman]

No - a reboot doesn't close the apps. It's because many of those apps are not really running, even though they appear in the multi-task bar. iOS removes most of them from RAM (system memory) and only a very few of the app's functions are left running - playing audio for example. The remaining apps that 'appear' to be running simply have their state ('context') stored so that the app can be reloaded in exactly the same state as when it was suspended. Those context files are not cleared by a reboot, so the apps still appear in the multi-task bar. The only way to delete the context file - and hence remove its app from the multi-task bar is to manually close the app by pressing an icon in the multi-task bar until they all start to jiggle and then pressing the upper left hand corner of the app's icon. That tells iOS to delete the app's context file and so it no longer appears in the multi-task bar......

Tim

Thanks Super Tim!

 

[daffie]

No - a reboot doesn't close the apps. It's because many of those apps are not really running, even though they appear in the multi-task bar. iOS removes most of them from RAM (system memory) and only a very few of the app's functions are left running - playing audio for example. The remaining apps that 'appear' to be running simply have their state ('context') stored so that the app can be reloaded in exactly the same state as when it was suspended. Those context files are not cleared by a reboot, so the apps still appear in the multi-task bar. The only way to delete the context file - and hence remove its app from the multi-task bar is to manually close the app by pressing an icon in the multi-task bar until they all start to jiggle and then pressing the upper left hand corner of the app's icon. That tells iOS to delete the app's context file and so it no longer appears in the multi-task bar......

Tim

Interesting read! However what suprises me is that whenever I have apps minimized and they still appear in the multitask-bar, they seem to still eat-up ( a lot of) RAM. I check with System Status app. The Memory Tab shows Free memory and when I decide to close the apps from the multitask-bar, then a lot of memory is free'd up...in other words more Free memory in System Status. For example whenever I have iCab open it will have some 40-50 Mb of mem in use. When I close iCab, then those 40-50 Mb are free'd up.

Maybe I'm missing something here, and you are able to educate me some more on this Thanks again.

 

[Tim SPRACKLEN]

The iPad's operating system, iOS, manages the RAM. If a new app needs to be loaded, and there's sufficient remaining free space in the RAM, then existing apps are left there untouched. This means they can be re-activated quickly. If, when iOS, tries to load a new app, there is insufficient space in the RAM, then iOS will unload an app to free up space for the new app to be loaded into.

Hence, in your example, if iCab is in the multi-task bar, it may well still be present in RAM as long as you've not had to load an app that would cause iOS to unload iCab. So, when you manually quit iCab, the RAM that it was occupying is freed up and you see the result of that.

But if you'd not used iCab for a while and have loaded several apps since you last used iCab then, chances are iOS will have unloaded iCab. Now, if you manually quit iCab it's already been removed from RAM by iOS and your 'quitting it' is only deleting iCab's context file. So, now, you'll see next-to-no RAM being recovered.

Tim

 

[daffie]

Very clear explanation, thanks very much. I know understand completely how memory management works on the ipad. Good to know that I can just leave things be and not manually close apps from the multitask bar everytime to free up ram. Totally unnecessary it seems.

 

[Tim SPRACKLEN]

I see no reason really. Of course, some functions - such as playing audio - are left active. You can see the list of iOS tasks that remain active when an app is suspended on the Apple iOS Development website. I never bother unless an app starts to 'misbehave', then closing it can 'clean things up' and gives you a 'fresh start'.

Tim

 

[daffie]

Why I kept closing apps manually is because it seems like the ipad is slowing down a bit whenever much is visible in the multitask bar. I could be mistaken of course, however it does seem like it. When the apps are "closed" then the system becomes a bit snappier.

 

[Tim SPRACKLEN]

For sure - if you've unloaded an app and freed up some RAM then, when you start another app off either (a) it's still in RAM because you unloaded other apps that were in RAM and so iOS could leave this particular app in RAM, so it starts faster because it doesn't need to be reloaded or (b) you've freed up RAM by unloading apps so, when you come to load another app, iOS doesn't need to unload an app that's already in RAM as you've already done this for iOS.

So your observations make perfect sense!!

Tim

 

[daffie]

Ah that does indeed make perfect sense! The logic behind it is definately there. I therefore assume apps that are still in RAM won't use any battery either, correct? Thanks again for all your help.

 

[Tim SPRACKLEN]

Generally speaking, you're right, though iOS does allow an app to keep some functionality active when it's suspended - I mentioned audio before, for example. So there is at least the opportunity for a suspended app to use some battery.

If you're interested in looking at multi-tasking in some more detail, there's an interesting presentation here....

http://labs.tranquilli.org/docs/iOS4_background_tranquilli.pdf

Tim

 

[daffie]

Tim...thanks! I will check out the document as well...

Edit : have read the document, but although I understand some parts, most of it is too technical for me personally. I understood your info much better