Just adding to Carlo’s informative response. How Mobile Multitasking Works The major new feature of Apple’s latest mobile operating system, iOS 4, is multitasking.
How you use it: When you press the Home button twice, Apple’s iOS 4 displays a “drawer” allowing you to switch between apps. The drawer shows your most recently used apps. This is similar to the “alt-tab” functionality we’re accustomed to on traditional PCs. What’s going on: When you leave an app in iOS 4, it’s not actually closing (unlike previous versions of the OS). Instead, it’s going into frozen, suspended animation, sitting inertly in the background. So when you relaunch an app, it opens instantly to pick up from where it left off before you “closed” it. That behaviour allows you to switch between apps very quickly — a feature called Fast App Switching, which is the core functionality of Apple’s iOS multitasking. (TidBITS has an excellent in-depth explanation of Fast App Switching.) Fast App Switching isn’t all iOS 4 multitasking does, as there are a few exceptions for specific types of apps. Apple allows apps that play audio, connect with voice-over-IP or use location detection to run quietly in the background while one thread is still active. So that’s why, for example, you can leave the Pandora app, and the music will still be playing in the background while you check your e-mail. Likewise, you can leave Skype while on a VoIP call, and you won’t hang up on your buddy while you’re browsing Safari, for example. Third, you can leave a mapping app or a fitness tracker like RunKeeper and come back to it, and it’ll still have a lock on your location. It’s up to third-party app developers, of course, to tell their apps to behave this way with the new iOS 4 software development kit. Another sort of background activity iOS supports is push notifications, which keeps a specific internet port active while the iPhone is in hibernation, so you can receive e-mails, instant messages and alerts even when the screen is off. These alerts pop up on the screen in the same way as SMS on the iPhone. WIRED Fast App Switching is indeed fast and stylish, avoids draining battery. All apps are constantly running inertly, so you can quickly switch between them all. TIRED Only allows a single application thread to continue running; only certain kinds of activities are allowed to run in the background. Push notifications scream for your attention at the centre of the screen. Multitasking in iOS4 is not like multitasking in OS X. All applications are not running at the same time. Only the active application in use is running. Any other applications on the multitask list are made inactive until you switch to one of them. It’s called cooperative multitasking. This is not the same as pre-emptive multitasking that is used in OS X. In this form of multitasking open applications can switch between active and inactive status automatically as needed and applications can run in the background. Because the iPhone and iPod Touches hold everything in memory multitasking does not demand much more power. Cheers, Ronni On 12/05/2011, at 10:56 AM, cm wrote: > Hi Shayne, > > Thanks for drawing our attention to the Activity Monitor Touch app. I will > get myself a copy. I do wonder, however, how HandyPadSoft can get away with > copying the Apple icon for Activity Monitor. > > I did notice in a few emails what could be misconceptions about background > apps on the iPhone and the iPad. Apart from a few exceptions noted below, > there is no penalty at all for having an app in the background. The Apple > engineers, as often they are, were very clever when they introduced > background apps to iOS. They in fact created a new paradigm to ensure that > while an app is available for immediate switching it is rarely using > resources. This ensures that the battery life of the iOS device will not be > negatively impacted and that memory will be freed up when required. > > Here is how it works. When an app goes into the background when say the user > presses the Home button or switches to a different app, execution for the app > is suspended. The app is given a few event cycles to save any data and record > any user choices. There is a framework where the app can be given limited, > intermittent processing time but these are exceptions that must be programmed > using specific frameworks. The examples of apps that continue with limited > processing time in the background are those that require location service - > such as GPS turn-by-tun applications, those that play music such as the iPod > app, or those that say accept incoming phone calls like Skype does. Of these, > only the location service, if it is poorly programmed, is a real problem. The > newly introduced in iOS 3 (I think it was) Push Notification, also means that > a program can remain suspended until there is work for it to do. > > If memory becomes short, background processes are terminated to free up > memory. The are closed down in reverse order of last access, so a program you > haven't used for two days, say, will be closed first. The program is given a > few event cycles to save user data and then its memory is released for reuse. > > So in principal at least, there is never any need to terminate an app unless > it has a limited form of background processing. The types of background > processing allowed are limited to few special cases. For most apps there is > no penalty at all for running in the background. A few poorly programmed > location apps can be a problem, but bad reviews will often tell you which > ones these are. > > Cheers, > Carlo > > > On 2011-05-12, at 10:19, S Beach wrote: > >> Now seems an appropriate time to mention this... >> >> I got this monitor app for my iphone a while back >> http://itunes.apple.com/us/app/activity-monitor-touch/id385619152?mt=8 >> at the time it was free on a promo but now $2.49 >> >> I ran it the other day and noticed that a lot of the memory was used up. I >> then double clicked the home button to see the apps running in the >> background - and there was quite a few. So I started closing them one by one >> and watching the memory usage bar go down. Interesting exercise. Once I had >> closed all the apps there was a lot more memory available (Surprise!). >> >> Of course there's no way of knowing how much resources the monitor app is >> using - so I closed that when I had finished too. >> (Note that this will not change the amount of storage memory used by all >> your songs, videos, photos etc; just the system memory.) >> >> So it is clear that it is well worth regularly checking what apps are >> running and closing any that are not needed. >> >> Doing this once or twice a day (for example - choose your own time period) >> would free up memory & help to keep things running smoothly and likely >> improve the battery life as well. >> >> Regards >> >> Shayne >> >> >> On Thu, May 12, 2011 at 7:32 AM, John Hatch <j...@iinet.net.au> wrote: >> >> Thanks Daniel. It solved the problem, also improved the performance as well. >> Is seems the ipad can become clogged with residual stuff and slow down >> >> Much appreciated >> For others the app was Autocadws - quite impressive app also "photo sort" app >> >> Cheers >> >> John >> >> Sent from my iPad >> >> On 12/05/2011, at 2:16 AM, Daniel Kerr <wa...@macwizardry.com.au> wrote: >> >> > >> > Not really an easy way to "see" what memory is used or free. >> > But generally, the easiest way to fix it is to turn the iPad off (Hold down >> > the power button til the "Slide to Power Off" comes up. >> > Then side to power it off, wait a few seconds and then power it back on >> > again. >> > That will "flush out" (or free up) the "memory". >> > >> > Kind regards >> > Daniel >> > >> > >> > On 12/5/11 2:13 AM, "John Hatch" <j...@iinet.net.au> wrote: >> > >> >> >> >> Does anybody know how much memory is on the ipad? Have an app that say not >> >> enough memory. How can you check to see what apps are running? >> >> >> >> John >> >> >> >> Sent from my iPad -- The WA Macintosh User Group Mailing List -- Archives - <http://www.wamug.org.au/mailinglist/archives.shtml> Guidelines - <http://www.wamug.org.au/mailinglist/guidelines.shtml> Unsubscribe - <mailto:wamug-unsubscr...@wamug.org.au>
