Definitions

Pervasive Computing

"a system where that networking logic becomes applicable in every realm of daily activity, in every location and every context."

http://en.wikipedia.org/wiki/Ubiquitous_computing

"the growing trend towards embedding microprocessors in everyday objects so they can communicate information.  The words pervasive and ubiquitous mean "existing everywhere." Pervasive computing devices are completely connected and constantly available."

http://searchnetworking.techtarget.com/definition/pervasive-computing

Both definitions imply that P.C. is the incorporation of technology in all areas of everyday use.


Ubiquitous Computing

"a post-desktop model of human-computer interaction in which information processing has been thoroughly integrated into everyday objects and activities."

http://en.wikipedia.org/wiki/Ubiquitous_computing

"technology is everywhere and we use it all the time."

http://www.rcet.org/ubicomp/what.htm

The first definition implies that U.C. is the frequent implementation of technology in everyday use, but the second one implies that it is all-encompassing.

Ambient Computing

"electronic environments that are sensitive and responsive to the presence of people."

http://en.wikipedia.org/wiki/Ambient_intelligence

"Ambient computing is concerned with issues of interface design and interaction arising from ubiquitous computing (Ubicomp) environments."

http://www.infoq.com/news/2010/07/ambient-ubiquitous-computing

Disappearing Computing

Disappearing computers is the idea of technologies which integrate themselves into daily life so well that they are indistinguishable from it.

http://smart-future.net/10.html

"A vision of the future is one in which our world of everyday objects and places becomes infused and augmented with information processing and exchange. In this vision, the technology providing these capabilities is unobtrusively merged with real-world objects and places, so that in a sense it disappears into the background, taking on a role more similar to electricity - an invisible pervasive medium."

http://c2.com/cgi/wiki?DisappearingComputer