THE COMPUTER FOR THE 21ST CENTURY

Mark Weiser was the chief technology officer at Xerox’s Palo Alto Research Center (Parc). He is often referred to as the father of ubiquitous computing. He coined the term in 1988 to describe a future in which invisible computers, embedded in everyday

objects, replace PCs. Other research interests included garbage collection, operating systems, and user interface design. He received his MA and PhD in computer and communication

science at the University of Michigan, Ann Arbor. After completing his PhD, he joined the computer science department at the University of Maryland, College Park, where he taught for 12 years. He wrote or cowrote over 75 technical publications on such subjects as the psychology of programming, program slicing, operating systems, programming environments, garbage collection, and technological ethics. He was a member of the ACM, IEEE Computer Society, and American Association for the Advancement

of Science. Weiser passed away in 1999.

Silicon-based information technology, in contrast, is far from having become part of the environment. More than 50 million personal computers have been sold, and the computer nonetheless remains largely in a world of its own. It is approachable only

through complex jargon that has nothing to do with the tasks for which people use computers.

“Ubiquitous computing” in this context does not mean just computers that can be carried to the beach, jungle or airport.

Even the most powerful notebook computer, with access to a worldwide information network, still focuses attention on a single box. Furthermore, although ubiquitous computers may use sound and video in addition to text and graphics, that does not make them “multimedia computers.” Today’s multimedia machine makes the computer screen into a demanding focus of attention rather than allowing it to fade into the background.

As computer scientists, my colleagues and I have focused on devices that transmit and display information more directly. We have found two issues of crucial importance: location and scale. Little is more basic to human perception than physical juxtaposition, and so ubiquitous computers must know where they are. If a computer knows merely what room it is in, it can adapt its behavior in significant ways without requiring even a hint of artificial intelligence.

The next step up in size is the pad, something of a cross between a sheet of paper and current laptop and palmtop computers. Robert Krivacic of PARC has built a prototype pad that uses two microprocessors, a workstation-size display, a multibutton stylus and a radio network with enough communications bandwidth to support hundreds of devices per person per room. Pads are intended to be “scrap computers” (analogous to scrap paper) that can be grabbed and used anywhere; they have no individualized identity or importance.

Prototype tabs, pads and boards are just the beginning of ubiquitous computing. The real power of the concept comes not from any one of these devices—it emerges from the interaction of all of them. The hundreds of processors and displays are not a “user interface” like a mouse and windows, just a pleasant and effective “place” to get things done. What will be most pleasant and effective is that tabs can animate objects previously inert.

The technology required for ubiquitous computing comes in three parts: cheap, low-power computers that include equally convenient displays, software for ubiquitous applications and a network that ties them all together. Current trends suggest that the first of these requirements will easily be met. Larger displays are a somewhat different issue. If an interactive computer screen is to match a white board in usefulness, it must be viewable from arm’s length as well as from across a room.

Computer operating systems and window- based display software will have to change substantially. This assumption is reasonable for conventional mainframes and personal computers, but it makes no sense in terms of ubiquitous computing. Pads, tabs and even boards may come and go at any time in any room, and it will certainly be impossible to shut down all the computers in a room to install new software in any one of them.

Data transmission rates for both wired and wireless networks are increasing rapidly. Access to gigabit-per-second wired nets is already possible, although expensive, and will become progressively cheaper. Yet the problem of transparently linking wired and wireless networks resists solution.

Although some stopgap methods have been developed, engineers must develop new communications protocols that explicitly recognize the concept of machines that move in physical space.

Present technologies would require a mobile device to have three different network connections: tiny-range wireless, long-range wireless and very high speed wired. A single kind of network connection that can somehow serve all three functions has yet to be invented.

Most important, ubiquitous computers will help overcome the problem of information overload. There is more information available at our fingertips during a walk in the woods than in any computer system, yet people find a walk among trees relaxing and computers frustrating. Machines that fit the human environment

instead of forcing humans to enter theirs will make using a computer as refreshing as taking a walk in the woods.

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