Refers to one kind of systemThis is a very generic term for any collection of components that, all together, can do something. Systems can be built from subsystems. Examples are your cell phone; your computer; the radio in your car; anything that seems like a "whole." that can behave as if it were another kind. A good example is a Macintosh, which, by itself, works very different from an Intel/Microsoft-based PC. But a Mac can pretend to be a PC by emulating how a PC works.
Inside the Internet of Things - Bryon Moyer Blog