iOS 4 is the name of the iPhone's operating system, and it's rolling out today for free. We expect to see it popping up when the California sun rises, so that's late afternoon UK time.
Your phone must be connected to your computer via USB to get the update from iTunes -- there are no over-the-air updates like on an Android phone. And you'll have to refresh your iTunes to get the new version of the iPhone OS, so why not fire up the tunage now and download the we told you about last week.
The iOS 4 updates adds some features iPhoners have been craving for ages, including the ability to change the wallpaper and sort your app icons into folders.
You'll also get a simple form of multitasking, so you could theoretically listen toin the background once the app itself has been updated to support multitasking. Additionally, there'll be a combined email inbox if you want to see all your emails in one place, and an iBooks app for buying ebooks from Apple.
iPhone 3GS and and third-generation iPod touch owners will see all the new features of iOS 4, while iPhone 3G and second-generation touch users will miss out on multitasking. Original iPhone owners get nothing, sadly.