Apple this week previewed the next generation of its iPhone software, which will add over 100 new features, include Multitasking for third party apps, to the iPhone, iPod Touch and iPad.

At the company's Cupertino, California headquarters, CEO Steve Jobs also announced an updated Software Development Kit which will provide programmers with over 1,500 new Application Programming Interfaces (APIs).

“iPhone OS 4 is the fourth major release of the world’s most advanced mobile operating system,” said Steve Jobs, Apple’s CEO. “We’re delivering over 100 new features, including multitasking, folders, a unified inbox, deeper Enterprise support, and an iPhone version of our iBooks reader and online iBookstore.”

Another new features include: the ability to created user defined folders for organizing apps; a unified inbox allowing users to see messages from all their email accounts displayed together in a single inbox; new gaming features; a new mobile advertising platform for developers to embed ads in their applications; and new enterprise features which will improve iPhone security and compatibility in corporate settings.

In revealing some of the new features, the company did say that not all the new features will not work on all products. Most notably, multitasking will only work on the iPhone 3GS and the third generation iPod touch with 32GB or 64GB of memory.

Apple says iPhone OS 4 will be available as a software update to iPhone and iPod touch users this summer. An iPad version of iPhone OS 4 will arrive in the fall.

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