If youre looking for app switching in the manner supported by iOS 4.0, Windows Phone will disappoint. Theres no Apple-like multitasking supported by the OS at launch. Windows Phone 7 doesnt totally regress in this regard. This is where the back button comes in.
The back button in Android literally takes you back screens until you land at your home screen, at which point it stops functioning. In Windows Phone, the back button is more like the back button in a web browser - it takes you back, in order, through every app/window youve visited.
Lets say youre typing a text message and you want to double check something you received in an email. Theres no conventional multitasking support so while youre in the messaging app youll hit the Start button, and tap the email tile to find the message you were looking for. Now to get back to your text message, in a conventional smartphone OS without multitasking youd hit the home/start button, and launch the messaging app again. Thats how it used to work in iOS. In Windows Phone however, hitting the back button will take you out of the email app and back to the last app you were in. In this case, that would be the messaging app.
There are rules for how the back button works. First, never use it after midnight. The history removes almost all references back to the Start screen with the exception of the most recent one. For example, if this is the path you took:
Messaging -> Start -> Email -> Start -> IE -> Start -> Zune
Continuously hitting the back button would take you to those screens in this order:
Zune -> Start -> IE -> Email -> Messaging
You always get the most recent Start screen in your history in case you, literally want to go back to the screen you were just at. Everything else however assumes that youll just hit the Start button if you want to go home and youll just traverse through apps youve visited.
The history doesnt grow by using the back button. For example, if you launch the messaging app, hit back and then launch your email, hitting the back button will only get you back to the Start screen.
It sounds like a complex series of rules but honestly it just works for the most part. The back button really shines when you launch an app from within another app. Then theres no going back to the Start screen, you just switch between the app youre currently at and the one you were at prior to it. Its like a one-tap task switcher.
The back button doesnt completely negate the need for iOS style multitasking, but it gets you around 90% of the way there. Copy & paste is the other glaring omission, but Microsoft has already committed to deliver clipboard functionality in early 2011. Weve privately seen a demo of the feature working, Microsoft is still ironing out the best way to make it happen within the Metro UI.
Windows Phone does support suspend/resume of apps. When you switch away from an app and later return back to it, the app will pick up where you left off - similar to what iOS4 enabled. All thats really missing is the ability for 3rd party developers to have portions of their code run in the background and some sort of task switching mechanism.
