Intel made its fortune on the chips that power personal computers, and Microsoft on the software that goes inside. Google's secret sauce is that it finds what you are looking for on the Internet. But the ground is shifting beneath these tech titans because of a major force: the rise of mobile devices.
These and other tech companies are scrambling to reinvent their business models now that the old model — a stationary customer sitting at a stationary desk — no longer applies. These companies once disrupted traditional businesses, from selling books and music to booking hotels. Now they are being upended by the widespread adoption of smartphones and tablets.
"Companies are having to retool their thinking, saying, 'What is it that our customers are doing through the mobile channel that is quite distinct from what we are delivering them through our traditional Web channel?' " said Charles S. Golvin, an analyst at Forrester Research, the technology research firm.
He added, "It's hilarious to talk about traditional Web business like it's been going on for centuries, but it's last century."
The industry giants remain highly profitable drivers of the economy. Yet the world's shift to computing on mobile devices is taking a toll, including disappointing earnings reports last week from Google, Microsoft and Intel, in large measure related to revenue from mobile devices. Investors are in suspense over Facebook's earnings to be disclosed Tuesday, for much the same reason. Yahoo's new chief, Marissa Mayer, said on Monday that Yahoo had failed to capitalize on mobile and must become a predominantly mobile company.
Demand for Intel chips inside computers — which are much more profitable than those inside smartphones — is plummeting. At Microsoft, sales of software for PCs are sharply declining. At Google, the price that advertisers pay when people click on ads has fallen for a year. This is partly because, while mobile ads are exploding, they cost less than Internet ads; advertisers are still figuring out how to make them most effective.
Since its initial public offering, Facebook has lost half its value on Wall Street under pressure to make more money from mobile devices, now that six of 10 Facebook users log in on their phones.
Making money will now depend on how deftly tech companies can track their users from their desktop computers to the phones in their palms and ultimately to the stores, cinemas and pizzerias where they spend their money. It will also depend on how consumers — and government regulators — will react to having every move monitored.
In addition, Nielsen found that only one in five smartphone users described ads on phones as "acceptable."
Today almost half of Americans own a smartphone, according to comScore — an astoundingly fast adoption since Apple introduced the iPhone just five years ago. The amount of time people spend on their phones surfing the Web, using apps, playing games and listening to music has more than doubled in the last two years, to 82 minutes a day, according to eMarketer; the time spent online on computers will grow just 3.6 percent this year.
"What has caught people off guard has been acceleration of the multitude of things that you can do with a smartphone," said David B. Yoffie, a Harvard Business School professor who studies the technology sector.
"The Web started in 1993, '94," he added. "It didn't disrupt everything for a decade and a half. The smartphone revolution started a half decade ago. Because of the existence of the Web, it allowed the phone to have a disruptive impact in a shorter time frame."
Still, mobile provides huge opportunities for these businesses, industry analysts say. That is largely because people reveal much more about themselves on phones than they do on computers, from where they go and when they sleep to whom they talk to and what they want to buy.
Consumers may be put off by the intrusion of marketers into their daily lives, but companies say the trade-off can be worth it — an unprompted calendar alert, say, that tells you whether you'll be late for a meeting or a coupon when you are near a shop.
"We're really starting to live in a new reality, one where the ubiquity of screens really helps users move from intent to action much faster and more seamlessly," Larry Page, Google's chief executive, told analysts last week. "It will create new opportunity in advertising."
Companies are addressing the challenges in different ways. Despite the disappointment in its recent earnings report, Google says it is on track to earn $8 billion from mobile ads, apps and media in the coming year, and has activated half a billion devices running its mobile operating system, Android. Google earns the majority of mobile ad dollars.
It is offering location-based ads, like a T-Mobile campaign that sent users ads when they were near stores. Some mobile ads already make more money than desktop ads, said Google's chief financial officer, Patrick Pichette.
But one of Google's biggest challenges is tracking whether people make a purchase after they see a mobile ad. Unlike online, where Google knows if someone buys a camera after searching for it, the company does not know if someone searches for a Thai restaurant nearby and then eats there.
That is why it is trying to follow people into the physical world, with services like Wallet for payments and Offers for coupons. Facebook is trying to use what it knows about its billion users to serve up ads on other applications they download on their phones. For instance, a soda brand that wants to target men in Los Angeles who like the Lakers could show them ads not only when they are logged into Facebook's mobile app, but on other apps as well.
"We think that showing mobile ads outside of Facebook is another great way for people to see relevant ads and discover new apps," the company said in response to an e-mail inquiry.
Not wanting to watch from the sidelines as people abandon computers for smartphones, Microsoft on Friday is introducing a version of its Windows software tailored for touch-screen devices and a new tablet, the Surface.
But Microsoft executives told analysts last week that the slowdown in computer technology was because of other factors besides mobile, like tough economic conditions and companies waiting to buy software until its new software, Windows 8, arrived.
Microsoft's chief executive, Steven A. Ballmer, called Windows 8 "the beginning of a new era at Microsoft."
Intel is playing catch-up by making chips for more than two dozen smartphones and tablets coming to market. The shift to mobile has also created a new market for Intel: Its chips are in the huge servers that power the cloud, where much mobile data is stored.
"As the market for smartphones and tablets evolved, the company historically didn't have a presence," said Jon Carvill, an Intel spokesman. "This year, that's started to change."
For other tech companies, mobile has been a boon from early on. Apple became the most valuable company in the United States selling the iPhone and iPad. Recently, Apple built its own mobile maps to replace Google's maps on the iPhone in part because it wanted to keep valuable information about users' location searches to itself and away from its competitor.
Nvidia and Qualcomm are making processors for mobile devices. Amazon and eBay are selling people things even on small screens. And mobile phone owners have found some services — like Zillow for real estate, Yelp for local businesses and OpenTable for restaurant reservations — better on phones than on computers, and revenue has followed.
For investors and others trying to solve the riddle of making money on mobile users, Marc Andreessen, the venture capitalist, extolled the virtues of the mobile era this way: "We're going to know a tremendous amount about people."