Multi-taskingChief among the improvements to iOS 4 is the introduction of multi-tasking, giving you the ability to run background tasks – like waiting for a file to download – while doing something else in the foreground. Sadly users of the 3G won't get this feature as, probably quite rightly, Apple thinks the phone is too slow to cope.
To start multi-tasking, you simply close the app you're currently running and start a new one. Double tap the home button and you're presented with a list of the apps running, allowing you to switch between them. Press and hold the icon and tap the cross to close an app. It's a neat and simple way of handling things and it's a very welcome addition to the platform. However, it isn't the be all and end all.
The multi-tasking actually works by allowing 'closed' apps access to certain core features of the OS – like music playback, file downloads, and GPS – so that they can tick along in the background but otherwise the app actually goes into a paused state. So while you can listen to Spotify while downloading a large file in Safari and writing an email, you can't have two application windows open at the same time or leave your character 'grinding' in a game while you do something else. Also very few existing apps, except for Apple's own, have been updated to support multi-tasking yet, so for the time being they will close as before when you press the home button and the link on the multi-tasking bar just acts as a shortcut to reopen them.
If you were wondering what happened to the iPod controls, which used to appear when you double-tapped the Home button, these are now accessed by swiping right when on the multi-tasking menu. These controls are also available if you're using other music-playing apps like Spotify or last.fm. As they don't have multi-tasking 3G users just get the conventional iPod controls of old.
FoldersIf multi-tasking was the big headline grabber for most people, it's surely folders that takes second place. Now, instead of swiping through half a dozen pages of icons to get to the apps you want, you can arrange them into neat themed folders like Games, Social, and Utterly Pointless But Seemed Like It Would Be Funny At The Time. To create a folder you simply hold down your finger on an icon to make them go wobbly then drag one icon on top of another. You can then change the name of the folder and drag more icons into it to add up to a total of 12 apps.
One oddity is that you can't just create a folder or turn an app into a folder, as it were. You can, however, remove apps from a folder to create a folder with one app in it that way. This is an addition available to all compatible devices.