The Apple Worldwide Developers Conference (WWDC) is a conference held annually by Apple Inc. The conference is primarily used by Apple to showcase its new software and technologies for developers, as well as offering hands-on labs and feedback sessions.

WWDC 2011 is being held at Moscone West, San Francisco from June 6 to June 10, 2011. The event reportedly sold out within 10 hours of the 5,000 tickets being placed on sale on March 28th, 2011. The ticket price also remained the same from the 2010 WWDC, selling at $1,599.

At the keynote, Apple CEO Steve Jobs unveiled a new Apple product- online cloud storage service- iCloud, which will be supported by new versions of applications including Mail, Contacts, Calendar and Music.

Apple said iCloud is a breakthrough set of free new cloud services that work seamlessly with applications on iPhone, iPad, iPod touch, Mac or PC to automatically and wirelessly store users content in iCloud and automatically and wirelessly push it to all user's devices.

Apple unveiled iOS 5, which includes Notification Center, iMessage, Newsstand, Twitter Integration among 200 new features. The iSO 5 will be available to iPhone, iPad and iPod touch users this fall.

iOS 5 has some great new features, such as Notification Center, iMessage and Newsstand and we can't wait to see what our developers do with its 1,500 new APIs, Apple's CEO Steve Jobs said.

Take a look at some of the pictures of day 1 at WWDC 2011: