SAN FRANCISCO — Steve Jobs, Apple chief executive officer, unveiled the company’s much-anticipated iPad tablet computer Wednesday, calling it a new third category of mobile device that is neither smart phone nor laptop, but something in between.

The iPad will start at $499, a price tag far below the $1,000 that some analysts were expecting. But Apple still must persuade recession-weary consumers who already have other devices to open their wallets yet again. Apple plans to begin selling the iPad in two months.

Jobs said the device would be useful for reading books, playing games or watching video, describing it as “so much more intimate than a laptop and so much more capable than a smart phone.”

The half-inch-thick iPad is larger than the company’s popular iPhone but similar in design. It weighs 1.5 pounds and has a touch screen that measures 9.7 inches diagonally. It comes with 16, 32 or 64 gigabytes of flash memory storage and has Wi-Fi and Bluetooth connectivity built in.

Jobs said the device’s battery can last for 10 hours and sit for a month on standby without needing a charge.

Sitting on stage in a cozy leather chair, Jobs demonstrated how the iPad is used for surfing the Web with Apple’s Safari browser. He typed an e-mail using an on-screen keyboard and flipped through photo albums by flicking his finger across the screen.

He also showed off a new electronic book store and a book-reading interface that emulates the look of a paper book. That puts the iPad in competition with Amazon. com’s Kindle and e-book store.

Tim Bajarin of Creative Strategies called the iPad a great multipurpose mobile device — and the first tablet with a chance of success with consumers. But Bajarin said Jobs’ presentation only touched the tip of what the iPad could do for newspapers, magazines and book publishers, three industries struggling in the transition to the digital age.

A new newspaper reader program from the New York Times and a game from Electronic Arts were demonstrated during the event. The iBookstore launched with titles from Penguin, Simon & Schuster, HarperCollins, Hachette Book Group and Macmillan, and will open up to other publishing houses.

Applause rang out as Jobs stepped onto the stage to introduce the iPad to hundreds of analysts, bloggers and other guests in the Yerba Buena Center for the Arts in San Francisco.

When he announced the price — lower than what had been speculated—it was accompanied by the sound of glass shattering.

Like iPods and the iPhone, the iPad can sync with Apple’s Macintosh and Microsoft’s Windows computers. Jobs said the iPad also will be better for playing games and watching video than either a laptop or a smart phone.

Unlike a laptop, the iPad has an accelerometer, so gamers can tilt the device to control what’s happening on the screen. And the iPad is lighter and easier to hold for long periods of time while watching a movie or TV show.

Its large screen makes touch-typing easier than on a smart phone, and it is extremely responsive to finger swipes and taps for scrolling through Facebook, photo albums and news articles. The iPad comes with software that includes a calendar, maps and video and music players. All seem to have been slightly redesigned to take advantage of the iPad’s bigger screen.

The basic iPad models will cost $499, $599 and $699, depending on the storage size, when the device comes out worldwide in March.

In the United States, Apple also will sell a version with data plans from AT&T: $14.99 per month for 250 megabytes of data, or $29.99 for unlimited usage. Neither will require a long-term service contract.

The iPad models that can connect to AT&T’s wireless network will cost more — $629, $729 and $829, depending on the amount of memory — and will be out in April. International cellular data details have not yet been announced.