Apple has previewed its iPhone (operating systems) OS 4 software and released a beta version of the software to iPhone developer programme members. The iPhone OS 4 beta release includes an updated software development kit (SDK) with over 1,500 new application programming interfaces (APIs) and over 100 new features that will be available to iPhone and iPod touch users this summer.

The new features include multitasking for third party applications; folders to better organise and access applications; improved mail with a unified inbox, fast inbox switching and threaded messages; enhanced enterprise support with even better data protection, mobile device management, wireless application distribution and more; Apples new iAd mobile advertising platform; and iBooks, the delightful new ebook reader and online bookstore recently debuted on the iPad.

iPhone OS 4 is the fourth major release of the worlds most advanced mobile operating system, said Steve Jobs, Apples Chief Executive Officer.

iPhone OS 4s new multitasking offers users a new way to quickly move between applications, and provides developers seven new multitasking services to easily add multitasking features to their applications. These services include background audio, so applications like Pandora can play music in the background.

iPhone OS 4 delivers the best mail experience on a mobile phone with its new unified inbox, allowing users to see messages from all their email accounts displayed together in a single inbox. In addition, users can now thread their messages by conversation, making it easier to stay on top of email discussions, as well as open email attachments with compatible apps from the App Store.

iAd, Apples new mobile advertising platform, combines the emotion of TV ads with the interactivity of web ads. iAd displays full-screen video and interactive ad content. iPhone OS 4 lets developers easily embed iAd opportunities within their applications, and the ads are dynamically and wirelessly delivered to the device.

Apple will sell and serve the ads, and developers will receive an industry-standard 60 per cent of iAd revenue.

The iPhone OS 4 beta release includes a developer preview of game centre, which contains a set of APIs that allows developers to create applications with the ability to invite friends to play a game, start a multiplayer game through matchmaking and track achievements and compare high scores on a leader board. Applications created with GameKit APIs will work with game centre, Apples new social gaming network available to iPhone and iPod touch users later this year.

New enterprise features in iPhone OS 4 include improvements in security, scalability and compatibility. The new mobile device management service can be integrated with third party servers to wirelessly configure, query and even wipe or lock managed iPhones, and iPhone OS 4 enables enterprises to securely host and wirelessly distribute their own in-house developed apps to employees.

The new Data Protection feature uses a users passcode as an encryption key to protect mail messages and attachments stored on the iPhone. iPhone OS 4 now provides the option to set a longer, more complex passcode, making iPhone and its data even more secure. iPhone OS 4 allows IT managers to set up multiple Exchange ActiveSync accounts, is compatible with Exchange Server 2010 and includes support for forthcoming SSL VPN applications from Juniper Networks and Cisco.

Today, more than four billion applications have been downloaded from the revolutionary App Store and more than 185,000 apps are available to consumers in 90 countries. Over 85 million iPhone and iPod touch users around the world can choose from an incredible range of apps in 20 categories, including games, business, news, sports, health, reference and travel.

The iPhone OS 4 beta software and SDK are available immediately for iPhone Developer Program members at developer.apple.com. iPhone OS 4 will be available as a software update to iPhone and iPod touch users this summer. A version of iPhone OS 4 will be coming to iPad this Fall.