Apple CEO Steve Jobs made only his second public appearance since going on medical leave in January to kick off the Apple Worldwide Developers Conference in San Francisco today.

His speech marked the beginning of Apple's weeklong conference intended to showcase Apple's innovations for the upcoming year.

The star of the show is Apple's iCloud, a new internet-based service that will allow Apple users to play music and access data from any Apple device.

Instead of data being stored on the hard drives of the devices themselves, it will be stored on iCloud in large servers that can be accessed from any Apple device through the Internet.

The iCloud will bring a new level of integration between devices; users will be able to take a picture with their iPhone, upload it to iCloud, and download it to all their devices.

The launch of the system represents what very well may be the next major step for the digital world; the complete integration of all devices and the removal of data storage from individual hard drives to internet servers.

Also to be unveiled at the conference this year is Apple's new operating system, Mac OS X Lion, which will combine many of the features of iPad with those of Apple notebooks to give users a more intuitive way to interact with their Apple computers.

Upgrades include the new Mac App store as well as programs designed to streamline Mac use like Launchpad - a new way to organize applications.

Lion will borrow features of the iPad like full-screen applications and the Multi-Touch system that brings more fluid and realistic gesture responses to Mac computers.

The conference will also showcase Apple's upgrades to the iPhone operating system. The fifth version of the iOS software is intended to compete with the fast-growing Android smartphone market. Android smartphones have been outselling iPhones and the new system will increase the competitiveness of Apple's trademark smartphone.

The launch of iCloud is also intended to bolster iPhone sales, since the new system will create a level of integration between Apple devices that has never before existed.