The next version of Apple's mobile operating system, iPhone OS 4.0, is set to finally allow third party applications to run in the background via an Exposé-like interface. Sources close to Apple have confirmed the presence of an OS X-like window management system that will allow users to switch between different applications running in the background.
"Those familiar with the design of iPhone 4.0 said that the user interface will resemble Apple's desktop Expose feature, in that a key combination -- reportedly hitting the Home button twice -- will trigger an expose-like interface that brings up a series of icons representing the currently running apps, allowing users to quickly select the one they want to switch to directly. When a selection is made, the iPhone OS zooms out of the Expose task manager and transitions to that app."
Exposé on Mac OS X currently resizes all open windows to fit the display, but because of the iPhone's smaller screen and its single window application design, Apple engineers decided instead to just use application icons to switch between different apps.
Since the iPhone unveiling back in January 2007, Apple has taken quite a bit of criticism for not allowing third party applications to run in the background. The XNU kernel in iPhone OS does currently provide preemptive multitasking, but Apple limits it to their own built-in apps like Safari or Mail. Competitors such as Palm WebOS, Google Android, Windows Mobile, RIM Blackberry OS, and Nokia's Symbian OS all have had the ability to run any app in the background, though Microsoft seems to be taking a different route with their upcoming Windows Phone 7 Series operating system.
Other features also reported to be present in OS 4 are a universal mailbox and the ability to pin individual contacts directly to the homescreen.
Apple is rumored to unveil the next iPhone and iPhone OS at their annual World Wide Developers Conference (WWDC) that they often hold in June. It was also reported a few days go that Apple would unveil a new CDMA-based "iPhone HD" with an Apple A4 SoC, 960x640 display, and a front facing camera on June 22.