At Apple, a tablet-like device has been many years in the making. Apple filed a patent related to a tablet device as early as 2000, according to a Thomson Reuters patent database. But development has come in fits and starts. Mr. Jobs killed the project twice in recent years, the first time because the battery life was too short, and the second time because there was insufficient memory, said one of the people familiar with the matter.

Though Apple doesn't discuss future products, many analysts expect its tablet to be a multimedia device that will let people watch movies and television shows, play games, surf the Internet and potentially read electronic books and newspapers. It is not clear whether the device will run the full Macintosh operating system or a version of the iPhone operating system. Apple watchers expect the tablet to debut at the end of this year or early next year.

Analysts say how well an Apple tablet sells will depend on price, which most believe will be between $399, the price of a high-end iPod touch, and $999, the price of the cheapest MacBook laptop. "As devices become more expensive, your ability to make them mass market declines," said Toni Sacconaghi, an analyst with Sanford C. Bernstein & Co.

The popularity of cheap and light computers under $500 known as netbooks has pressured Apple to come out with a device in a similar price range. But as recently as last October, Mr. Jobs rejected the idea of a cheaper computer in an earnings call, saying, "We don't know how to make a $500 computer that's not a piece of junk."

Steve Jobs, who has been on medical leave from Apple Inc. since January to treat an undisclosed medical condition, received a liver transplant in Tennessee about two months ago. The chief executive has been recovering well and is expected to return to work on schedule later this month, though he may work part-time initially. Mr. Jobs didn't respond to an email requesting comment. "Steve continues to look forward to returning at the end of June, and there's nothing further to say," said Apple spokeswoman Katie Cotton.

When he does return, Mr. Jobs may be encouraged by his physicians to initially "work part-time for a month or two," a person familiar with the thinking at Apple said. That may lead Tim Cook, Apple's chief operating officer, to take "a more encompassing role," this person said. The person added that Mr. Cook may be appointed to Apple's board in the not-too-distant future.

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The specifics of Mr. Jobs's surgery couldn't be established, but according to the United Network for Organ Sharing, which manages the transplant network in the U.S., there are no residency requirements for transplants. Having the procedure done in Tennessee makes sense because its list of patients waiting for transplants is shorter than in many other states. According to data provided by UNOS, in 2006, the median number of days from joining the liver waiting list to transplant was 306 nationally. In Tennessee, it was 48 days.

The big question now among Apple's business partners, investors and fans: Will Mr. Jobs make his reappearance at Apple's annual software developers' conference next week in San Francisco, possibly to unveil a new iPhone?

Mr. Jobs, a survivor of pancreatic cancer, went on medical leave in January. He had earlier exhibited significant weight loss, and cited a nutritional problem related to a hormone imbalance. The unexpected departure, and the few details about Mr. Jobs's ailment, left some investors worried about whether he would return.

Since then, Apple hasn't provided any updates on Mr. Jobs's health. While Mr. Jobs has been on sick leave, some Apple directors have gotten weekly updates about his medical condition from the CEO's physician, according to a person familiar with the matter. Mr. Jobs's recovery "is coming along" and he is on schedule to return to work later this month, said this person, who has seen Mr. Jobs in recent weeks.

"He was one real sick guy," added this person. "Fundamentally he was starving to death over a nine-month period. He couldn't digest protein. [But] he took corrective action."

More than three months into a medical leave from Apple Inc., Chief Executive Steve Jobs remains closely involved in key aspects of running the company, say people familiar with the matter. Chief Operating Officer Tim Cook runs the day-to-day operations at Apple, these people say. But Mr. Jobs has continued to work on the company's most important strategies and products from home, they say. He regularly reviews products and product plans, and was particularly involved in the user interface of the new iPhone operating system that Apple unveiled last month, these people say.

Apple co-founder Mr. Jobs, who is considered the company's creative leader, is also involved in the development of future projects, they say. People privy to the company's strategy say Apple is working on new iPhone models and a portable device that is smaller than its current laptop computers but bigger than the iPhone or iPod Touch.

Mr. Jobs, who was treated in 2004 for a rare form of pancreatic cancer, took a medical leave in early January, saying he would return in June and would remain involved in "major strategic decisions while I am out." But he has made no public appearances or statements since then, and it has been unclear just how involved he continued to be. Apple has been mum about how Mr. Jobs's absence is affecting daily operations. Mr. Jobs didn't respond to requests for comment. Apple spokesman Steve Dowling said: "Steve continues to look forward to returning to Apple at the end of June."

In a letter to Apple employees released after markets closed on Wednesday, Mr. Jobs said that curiosity over his personal health "continues to be a distraction not only for me and my family, but everyone else at Apple as well."

Mr. Jobs said he had asked Tim Cook, Apple's longtime chief operating officer, to take on responsibility for Apples' day-to-day operations. "As C.E.O., I plan to remain involved in major strategic decisions while I am out. Our board of directors fully supports this plan," Mr. Jobs added.

For the first time in a decade, I'm getting to spend the holiday season with my family, rather than intensely preparing for a Macworld keynote.

Unfortunately, my decision to have Phil deliver the Macworld keynote set off another flurry of rumors about my health, with some even publishing stories of me on my deathbed.

I've decided to share something very personal with the Apple community so that we can all relax and enjoy the show tomorrow.

As many of you know, I have been losing weight throughout 2008. The reason has been a mystery to me and my doctors. A few weeks ago, I decided that getting to the root cause of this and reversing it needed to become my #1 priority.

Fortunately, after further testing, my doctors think they have found the cause-a hormone imbalance that has been "robbing" me of the proteins my body needs to be healthy. Sophisticated blood tests have confirmed this diagnosis.

The remedy for this nutritional problem is relatively simple and straightforward, and I've already begun treatment. But, just like I didn't lose this much weight and body mass in a week or a month, my doctors expect it will take me until late this Spring to regain it. I will continue as Apple's CEO during my recovery.

I have given more than my all to Apple for the past 11 years now. I will be the first one to step up and tell our Board of Directors if I can no longer continue to fulfill my duties as Apple's CEO. I hope the Apple community will support me in my recovery and know that I will always put what is best for Apple first.

So now I've said more than I wanted to say, and all that I am going to say, about this.

Although the company will not publicly confirm the arrival of a second iPhone, Apple watchers have concluded that a new version will be introduced June 9, the opening day of Apple's Worldwide Developers Conference. Apparently in preparation for the event, stocks of the existing iPhone have been dwindling in the last month.

Although AT&T stores still have phones in stock, according to a company spokesman, the supply has largely dried up in Apple's retail outlets, and the phones are no longer available through the company’s online store. Apple may be trying to avoid the anger it faced last September when it cut the iPhone's price by $200 just two months after it went on sale, making early buyers feel cheated. Mr. Jobs offered those customers a $100 store credit. Cutting down on supply means fewer angry buyers when their new phone is suddenly obsolete. “You can say what you want about Steve Jobs, but he's learning from his mistakes,” said Roger Entner, a senior vice president at IAG Nielsen, a market research firm. "They are cleaning out the supply channel." Even as supplies shrink, Apple has been signing a series of deals with cellphone network providers around the world. On Tuesday the cellular operator TeliaSonera said it would offer the iPhone in seven countries, including Sweden, Norway and Denmark. The only major countries without an iPhone distribution agreement are Japan, Russia and China.

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Both Mr. Jobs and Randall L. Stephenson, the chief executive of Apple's partner AT&T, have promised a new iPhone model this year that would run on a high-speed wireless data network. AT&T is building such a network, which uses technology known as 3G and is intended to support a range of new applications, including mobile digital video. The company said last week that the network would be largely finished by the end of June. But analysts say faster downloads may not be enough to touch off a new wave of consumer interest in the iPhone.

"Subscribers don’t care what the radio interface of their cellular phone is," Mr. Snyder said. If he is to rekindle the excitement that greeted the iPhone's introduction, Mr. Jobs is likely to need something else. So far, he has been successful in hiding any surprise features from the dozens of Web sites and bloggers that track the company's new products. There has been speculation about a higher-resolution camera, possible support for digital video recording, a slightly bulkier and more curved case, and the addition of a global positioning system receiver that would allow new Web services tied to a person’s location.