By JOHN MARKOFF

The cellphone is the world’s most ubiquitous computer. The four billion cellphones in use around the globe carry personal information, provide access to the Web and are being used more and more to navigate the real world. And as cellphones change how we live, computer scientists say, they are also changing how we think about information.

It has been 25 years since the desktop, with its files and folders, was introduced as a way to think about what went on inside a personal computer. The World Wide Web brought other ways of imagining the flow of data. With the dominance of the cellphone, a new metaphor is emerging for how we organize, find and use information. New in one sense, that is. It is also as ancient as humanity itself. That metaphor is the map.

“The map underlies man’s ability to perceive,” said Richard Saul Wurman, a graphic designer who was a pioneer in the use of maps as a generalized way to search for information of all kinds before the emergence of the online world.

As this metaphor takes over, it will change the way we behave, the way we think and the way we find our way around new neighborhoods. As researchers and businesses learn how to use all the information about a user’s location that phones can provide, new privacy issues will emerge. You may use your phone to find friends and restaurants, but somebody else may be using your phone to find you and find out about you.

Digital map displays on hand-held phones can now show the nearest gas station or A.T.M., reviews of nearby restaurants posted online by diners, or the location of friends. In the latest and biggest example of the map’s power and versatility, Google started a location-aware friend-finding system called Latitude in 27 countries early this month.

On its face, Google’s new service — available on dozens of mobile systems — is simply a way for friends to keep track of one another and meet up, for families to stay in touch or for parents to find comfort in knowing where their children are.

But it will generate a gold mine of new information about where millions of people travel each day, and there is no doubt that Google and others are planning to dig in that mine. “Everyone is watching Google, and this will open a floodgate of location-oriented applications and services,” said Greg Skibiski, the chief executive of Sense Networks, a New York City firm that mines the millions of digital trails left by cellphone users for marketing purposes.

It was the arrival of the so-called WIMP interface — for windows, icons, menus, pointer — in the 1980s on both the Apple Macintosh and computers using Microsoft Windows that made personal computers personal and moved them beyond the world of hobbyists and business. Now many of the software designers who created those interfaces say they see a change of similar magnitude with phones and maps.

“We’re way early on, and we don’t know what the Macintosh of maps will be yet,” said Paul Mercer, a former Apple Computer software designer who more recently worked on the development of the Palm Pre smartphone. “But because of their relationship to the real world, maps will be a metaphor for a huge swath of mobile computing.”

Indeed, a new generation of smartphones like the G1, with Android software developed by Google, and a range of Japanese phones now “augment” reality by painting a map over a phone-screen image of the user’s surroundings produced by the phone’s camera.

With this sort of map it is possible to see a three-dimensional view of one’s surroundings, including the annotated distance to objects that may be obscured by buildings in the foreground. For starters, map-based cellphones simply translate paper maps into a digital medium, but future systems will probably begin to blur the boundaries between the display and the real world.

“I always said the next interface would be Quake,” said Steve Capps, one of the designers of the original Macintosh interface, referring to the popular video game. “How long will it be before you come out of the subway and you hold up your screen to get a better view of what you’re looking at in the physical world?”

Increasingly, phones will allow users to look at an image of what is around them. You could be surrounded by skyscrapers but have an immediate reference map showing your destination and features of the landscape, along with your progress in real time. Part of what drives the emergence of map-based services is the vast marketing potential of analyzing consumers’ travel patterns. For example, it is now possible for marketers to identify users who are shopping for cars because they have traveled to multiple car dealerships.

“When I go from point A to point B with my feet, there is something of real value there,” said Tony Jebara, a Columbia University computer scientist who is a co-founder of Sense Networks.