Making many computers available throughout the physical environment, while making them effectively invisible to the user.
Ubiquitous computing is held by some to be the Third Wave of computing.
The First Wave was many people per computer, the Second Wave was one person per computer.
The Third Wave will be many computers per person.
Three key technical issues are: power consumption, user interface, and wireless connectivity.
The idea of ubiquitous computing as invisible computation was first articulated by Mark Weiser in 1988 at the Computer Science Lab at Xerox PARC