Ultralight Laptop

SAN FRANCISCO — Steven P. Jobs, Apple’s chief executive, took several big gambles Tuesday, betting that he could repeat his success in selling digital music by persuading Hollywood to allow Apple to rent digital movies, while at the same time returning to his original Macintosh roots with an elegant — but limited — ultralight computer called the MacBook Air.

Mr. Jobs has made his keynote presentation at the opening of the Macworld Expo trade show here a consistent marketing tour de force in recent years. And although Mr. Jobs did not return to the heights of media frenzy that he reached with the introduction of the iPhone a year ago, his presentation on Tuesday trod familiar, and popular, ground.

While introducing products and services from Apple’s best-known areas, Mr. Jobs concentrated on the movie rental service and the new notebook computer.

The terms of the service are similar to those offered by other companies. In an interview after the speech, Mr. Jobs insisted that Apple was the first distributor to persuade all of the major studios to join in its rental strategy. But the risk for Apple is that consumers may not like the limits placed on their movie viewing.

For the iTunes movie rentals, consumers will have 30 days to begin watching, then 24 hours to finish the movie before it is erased from the hard disk. Mr. Jobs said that after extended negotiations both sides felt this was an obvious strategy.

The movie studios, he said, knew it was time: “We talked to them and talked to them and finally a bit flipped. They know the rental model; we came to the conclusion it was the right model. It took months and it took a lot of discussions, but it wasn’t really that difficult once the bit flipped.”

In that interview, Mr. Jobs took pride in demonstrating the MacBook Air, a three-pound notebook computer that will sell at a base price of $1,799. Mr. Jobs said that in order to reach his goal of making the industry’s thinnest computer, Apple’s designers made a series of trade-offs that the majority of laptop buyers may not appreciate.

The computer uses a 1.8-inch disk drive, on which no more than 80 gigabytes of data can be stored. Memory is limited to a standard two gigabytes of RAM and its processor is slower than those of Apple’s other laptops. The design team jettisoned an optical disk storage device for playing DVDs. Mr. Jobs demonstrated a feature called Remote Disk that will make it possible to play the contents of a DVD via a wireless network from another Macintosh or Windows PC. Also, the MacBook Air’s battery is not removable.

Responding to a question about the growing array of media, including digital photographs, movies and music, that now swell most users’ hard drives, Mr. Jobs said, “Maybe this isn’t the computer for you.”

In the interview, Mr. Jobs chastised the recording industry for its efforts to handicap Apple and iTunes by offering digital music without digital rights management copy protection through competitors like Amazon.

“They’re trying to create a competitor to iTunes by denying us D.R.M.-free music,” he said. He noted, however, that because one major label, EMI, and independent music producers are selling D.R.M.-free music through Apple, iTunes customers now have access to what he said was about 35 percent of the market without copy protection.

“It’s been frustrating us a little,” he acknowledged. “The music industry and iTunes need to find a way to work together because we’re the best vehicle they have.”

During his presentation, Mr. Jobs also demonstrated the first major software upgrade for the iPhone. He surprised analysts by reporting that Apple sold four million iPhones during their first six months on the market, a number significantly above most market research firms’ projections.

He demonstrated a handful of features that have been added to the phone, including a navigation feature that allows the phone to find the user’s rough location on a map by using network databases that record the location of cellphone towers and Wi-Fi hot spots.

Apple shares slipped, losing $9.74, or 5.5 percent, to close at $169.04. In after-hours trading, shares fell another 3.6 percent.