Apple CEO Steve Job is set to deliver his keynote address at the Apple Worldwide Developers Conference at the Moscone Center in San Francisco at 10 a.m. PST.

Jobs is expected to announce the iCloud system that will distribute video, music and other resources, including user-uploaded files.

The other will be Apple's upgrade of its operating system for Mac computers. The latest product is known as OS X Lion, that will likely include user interface upgrades used on the company's highly successful tablet and phone operating systems.

The last major product is iOS 5, the latest iteration of the company's tablet and phone operating system. The new system will be crucial in its marketplace battle against Google's Android operating system for mobile phones and tablets.

There have previously been surprise announcements at WWDC. Previous such announcements have included the original iMac in 1998, the original iPod in 2001, and the iPhone in 2007.

Jobs' speech will mark his first public appearance since February when he introduced the iPad 2.

Jobs has mostly been away from the company since January when he went on medical leave to focus on my health.

Jobs has been involved in making major strategic decisions since then, leaving the responsibility of day-to-day operations to Tim Cook, the company's Chief Operating Officer.

I love Apple so much and hope to be back as soon as I can, Jobs said on January 17.

At WWDC, he's back again, for at least one day.