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As Steve Jobs took the stage in California for the company's annual developer conference, the Apple faithful collectively held their breath -- what would the tech genius show off today?

Many details of Apple's next-generation iPhone were already widely known, but expectations were nonetheless sky-high for the fourth-generation smartphone's official unveiling Tuesday at Apple's Worldwide Developers Conference (WWDC).

Jobs did not disappoint, unveiling a new phone operating system called iOS4, video conferencing capability, and a next-gen phone with new hardware tech fans are sure to drool over.

Calling it "beyond a doubt the most precise thing, and one of the most beautiful we've ever made," Jobs brought forth the new iPhone, which he said was 24 percent thinner than the previous 3GS model. The device, which looked like a polished version of the phone Gizmodo introduced the to the world in mid April, includes a front-facing camera and a slew of technology innovations.

The iPhone 4 comes in two colors, white and black, and will cost $199 for a 16GB version, and $299 for a 32GB model.

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The new phone has a display technology that Jobs branded "the Retina Display." He described the new display as better than OLED, which many predicted would be the future of gadget display tech. Instead, it is a form of LCD that Apple has optimized with an unusual 326-dpi resolution.

He told the audience, "Your apps look even better, but if you do a little bit of work, then they will look stunning. So we suggest that you do that."

Jobs stumbled briefly connecting a phone to the network in the convention hall for a live side-by-side demo of image quality from that new screen. But the 3.5-inch, 960 x 640 pixel display was clearly quite impressive. Later he attributed the glitch to the prevalence of over 570 Wi-Fi hotspots in the room -- a testimony to the crowd's enthusiasm.

Jobs highlighted several other bits of new hardware -- including an integrated three-axis gyroscope and a 5-megapixel camera with an integrated LED flash -- before moving on to the main attraction: iPhone OS 4.0, or iOS4.

The newest version of the software that powers the iPhone includes iBooks and finally incorporates multitasking, allowing a user to run several apps simultaneously, a limit that had infuriated owners of earlier models. A nearly final version of the software was released to developers at the show; the final version will ship June 21.

And iOS4 comes with "one more thing": video conferencing, through an app called FaceTime. Despite continued networking glitches (which Jobs laughed off as due to the number of Wi-Fi devices in the audience), he demonstrated the new tech by placing a call to Jonathan Ives, the long-time Apple designer responsible for much of the company's iconic hardware.

Video chats are limited to Wi-Fi for the time being, until Apple talks pricing with the network carriers, and the software places calls only to other fourth-gen iPhones ... again, for now.

The software will be available on June 21 to current iPhone owners, a free upgrade for everyone -- even iPod Touch users will finally get free upgrades. (In the past, Touch owners were forced to pay for upgrades that were free to iPhone owners.)

The company also formally unveiled the iAd platform. Jobs explained that “Apple hosts and sells the ads, so all you have to do is tell us where you want them and make the money.”

Jobs began the day by touting the success the company has had with the iPad. The company has sold over 2 million devices so far -- "That's one every 3 seconds," Jobs crowed. Those early adopters have purchased 35 million apps, or 17 per iPad. And with 15,000 apps submitted so far, there has been no shortage to chose from.

"We get about 15 thousand apps submitted every week. They come in up to 30 different languages. And guess what: 95 percent of the apps submitted are approved within 7 days," Jobs told the assembled crowd.

The Moscone Center in California had filled up early in the morning as Apple developers, fans and journalists poured in for the annual event, and Twitter feeds overflowed all day with enthusiasm and energy, notably when Jobs announced that the popular Netflix app would be coming to the iPhone, at some point in the summer.