Meanwhile, the Android OS and Palm Web OS have supported multitasking just fine for over a year. However, each platform handles multitasking quite differently. Lets take a closer look at how each mobile OSs multitasking works.
How you use it
When you press the Home button twice, Apples 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 were 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 behavior allows you to switch between apps very quickly a feature called Fast App Switching, which is the core functionality of Apples iOS multitasking. (TidBITS has an excellent in-depth explanation of Fast App Switching.)
Fast App Switching isnt 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 thats 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 youre browsing Safari, for example.
Third, you can leave a mapping app or a fitness tracker like RunKepper 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 center of the screen.
How you use it
Hold down the Home button and a tray appears showing the apps running in the background. Switch to another app and it instantly opens.
What's going on
Androids multitasking behavior is by far the most complicated to explain.
For more information contact All About Jazz.
