Cupertino-based software developer Apple will update the operating system that powers the iPhone to version 4.0 this June. But this is not to say that Apple is keeping the functionality that iPhone OS 4.0 will have to offer a secret. Quite the opposite- the company has recently showcased the operating system to the media.

The good news is that iPhone OS 4.0 comes with a multitude of changes – some 100 new features. I’ve picked the bits and pieces I considered to be more interesting. Here are the iPhone OS 4.0 highlights:

• Multitasking and app freezing

Double click the home button and a list of running apps is displayed. Select a running app to switch to it. Take Skype for example. In the past when you navigated away from Skype, the app would just quit. Now it can run in the background. You can switch to another app, then return.

When you close an app you can freeze said app. This way when you reopen it, they are in the exact state they were in when you closed them,

• Local notifications

Send notifications from one app on the iPhone to another app on the iPhone. Say you’re using an app, then switch to another. In the “another app” you will receive a notification that something is up in the first app.

Take the Skype example above. When Skype is running in the background and you receive a call, you'll see a notification on the screen. A single tap is enough to take that call.

• 5x digital zoom

This one is self explanatory

• App folders

Sort apps into folders. A folder is automatically created when you drag one app icon onto another. The folder is also named automatically – the name depends on the App Store category of that app.

• Game center

A centralized gaming service that connects games to one another. This service will be rolled out by the end of the year. It is similar to the PSN or Xbox Live multiplayer network.

• New Mail App

The new mail app features the following: unified inbox, fast inbox switching, multiple Exchange accounts, threaded messages.

• iBooks

Ebook reader and ebook store – the same from the iPad.

• Customizable backgrounds

Select the background your iPhone will use, just like jailbreakers have been able to do for quite some time.

• Bluetooth keyboards

The iPhone OS 4.0 will support Bluetooth keyboards

• New APIs

1500 new APIs

• iAd advertising

Users will be shown interactive ads within apps. This feature will be added later this year. It is part of the iPhone OS 4.0 developer tools.