Multitasking is generally understood as the ability of an operating system to run several applications at once. While the definition is fairly simple, as we've seen with releases of Android OS and Apple iOS4, the reality can be significantly more complex.
While the basic idea behind multitasking is the same on your smartphone as it is on your PC, how it works--both under the hood and in terms of the interface--can be drastically different.
A Mobile Multitasking Primer
When it comes to mobile operating systems, "multitasking" is used to refer to two separate features: The ability to run applications in the "background" (that is, apps running behind the current app, as is the case on a PC), and the ability to save the state of apps to disk (effectively pausing them).
Generally speaking, apps that continue to run in the background require more system resources (memory, processing power, etc) than an app that has been "paused," so managing these behaviors can be critical to keeping your smartphone responsive, and preventing its battery from draining too quickly.
A simple example might be a music-playing application; you'll probably expect it to continually run in the background, playing music, regardless of what other apps you've opened since you started playing music. On the other hand, a calendar application may only need to to be updated every few minutes to check for upcoming appointments. In between periodic updates, the app may be paused rather than continue to actively consume resources.
Multitasking on iOS 4 and Android Compared
In its most recent iteration, Apple's iPhone OS (iOS4) now includes support for more multitasking behaviors, which had been one of the most-requested features since the release of the original iPhone in 2007.
Meanwhile, in 2008 the HTC G1 (aka "Dream") was released with the first release of the Android OS, featuring native multitasking--including support for apps that run in the background--which at the time the iPhone lacked.
To make matters worse, Apple had been cracking down on hackers that released unofficial "jailbreak"
versions of the iPhone OS that featured more robust multitasking than what Apple offered. It seemed to many that Apple was fundamentally opposed to multi-tasking, and if one were to believe that, it might seem as if they have added multitasking under pressure from Android.
From a technical perspective, multitasking in iOS4 is markedly different than what is featured in Android. As with many technologies adopted by Apple, multitasking in iOS4 has been implemented with a very specific user experience in mind.
Android lets the entire app continue to run in the background. A good example is the Nintendo emuators by Youngh. If you use one of these apps then switch to something else, it'll keep running in the background, sound and all, until you decide to close it or your phone runs out of memory.
On the other hand, iOS4 lets apps keep certain features running in the background (but not full apps; for example, you'll be able continue a Skype call or keep listening to your Pandora station while using another app, but the full app isn't running), have its state saved (as with previous versions of the iPhone OS), both, or neither, as desired. In this sense it could be argued that the iPhone OS has always supported multi-tasking via state-saving, and this most recent addition is simply one more tool for developers used to tweak how their app is experienced.
To you, the user, this appears as a list of running applications, both "backgrounded" and "paused." Now iOS users are free to stream internet radio, chat, and browse GeekTech, all at the same time, regardless of how detrimental it may be to battery life.
As for comparisons between the multitasking implementations on Android OS and iOS4; The two are subtly, but fundamentally different. With Android, the operating system itself controls much of the multitasking, while iOS4 allows developers to choose how their app behaves.
Apple can take its more limited approach because it only has to support a few hardware configurations and so it can use a more narrowly-focused multitasking implementation, as compared to the myriad devices that feature the Android OS. Both approaches are well-informed, both work well, and ultimately, they are both fairly similar in their presentation to the user.
Which is Better? It Depends.
Which should you have in your pocket; an Android device or an iPhone? As it turns out, multitasking support may be one area where the two platforms have the most in common, even pre-iOS4! As such you may want to evaluate other features first, like which platform has the apps you want, which fits better in your pocket, or which looks better on your desk.
Update June 28, 2010; 10:10 AM PDT: Headline changed to better reflect the story's focus.
GeekTech blogger Christopher Head is a researcher at the Center for Research in Computing and the Arts .
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