This is something I’ve wondered about since iOS 4.How does iOS handle the recently running apps bar in terms of memory, CPU and background tasks. I caught this post by Fraiser Speirs a couple of days ago: Misconceptions About iOS Multitasking.
John Gruber over at Daring Fireball sums it up like this:
The system suspends apps running in the background automatically. The system removes suspended apps from memory automatically, when needed. Manually zapping all apps from this list is a voodoo placebo. The whole point of iOS’s multitasking model is that you, the user, should not have to worry about managing which applications are running and which are not. If you were supposed to do that, apps would have a Quit command. They don’t. You just go home, and the system should take care of the rest.
I’ve cleared my apps from the recently running bar more than a few times. When you double click the Home button on an iPhone, iPad or iPod Touch running iOS 4 or later, the interface slides up to reveal a bar of recently run apps. If you touch and hold on an icon in this tray, the icons will start to quiver and a red X will appear, allowing you to “quit” the app. I used to nuke any app that continues to use the GPS when I’m done with it and with early versions of the Skype app. Sounds like those were unnecessary steps.
Here is Apple’s support page about multitasking. It has the official party line and links to other useful tips.
I’m learning every day!