The new multi-tasking function in iOS 4 is one of the most anticipated features in the just released firmware. How does it work you ask? Well, buckle up kids, here we go. (hint: it's really easy!)
Essentially this is how it works:
You have one app open, say Twitter and have a number of tweets to catch up on. Quickly double click the home button on the face of the iPhone and the screen will lift up and grey out to reveal a tool bar. This tool bar shows all of your recently opened apps. Use your finger to swipe left or right to navigate through the icons.
Now simply click on the app you want to open and it will (cooly!) rotate into the foreground. Presto, you are working in a new app, the other still available in the back ground.
Need proof? Reverse it, double click home, navigate to back Twitter and reopen it and you are back at the same place you left it. It does not reload automatically!
Nifty trick, double click home to multi-task and swipe to the left brings you to a portion of the bar that contains iPod controls, and an orientation switch. This control will freeze the iPhone in the orientation you have it in. Especially handy when you have something you want to read, say in the newly dropped iBooks app for the iPhone.
Interestingly, if you are using an app in landscape mode and double click to multi-task, the bar does not appear in landscape mode. It is married to its position next to the home button.
What if you want to close an apps that is running in the back ground? double click the home button to get to the multi-task bar, then simply hold the app down until it wiggles, just as you would to delete it, and hit the red minus tag. Notice its a minus not an X? This does not delete the app, it just closes it, stops it from running in the background. I assume this will be handy, for several things, for instance you might not want that Instant Messaging program always running! Could potentially be embarrassing. Just saying.
The multi-tasking functionality is one of our favorite new tools. The entire toolset in iOS 4 makes this almost and entirely new phone. It is really something.
Sadly, it's apparent after using this on the iPhone, just how sorely the iPad needs this feature.