A coffeemaker, Biosphere 2 and the Universe sort neatly into three kinds of system
Your coffeemaker swaps both matter and energy with its surroundings, which makes it an open system, like a car or planet Earth. A computer or the Biosphere 2 project trades energy but not matter, so it counts as closed. Only an isolated system exchanges nothing at all, and the textbook candidate is the whole Universe.
A system is a set of connected parts that follow rules and together form one whole, defined by its boundary, structure and purpose. The word comes via Latin from the Greek systema, a whole built from several members. Drawing the boundary is the first move: it decides what counts as inside and what belongs to the environment. The parts must genuinely work together, or what looks like one system is really two or more.
The idea took scientific shape with steam. In 1824 the French physicist Sadi Carnot studied the working substance in a steam engine, usually water vapour, as it touched a boiler, a cold stream or a piston it could push. Rudolf Clausius widened the picture in 1850 to include the surroundings. A century later the biologist Ludwig von Bertalanffy proposed laws meant to hold for any system whatever its parts, and Norbert Wiener and Ross Ashby brought mathematics to control and communication under the name cybernetics. Walter Buckley coined the phrase complex adaptive system in 1968.
An open system can be treated as a black box that turns inputs into outputs, and outputs need not be objects. A passenger ship's output is people moved from one port to another. Systems nest, too: a subsystem is itself a system inside a larger one, as with IBM's mainframe job entry subsystems, which handled input, scheduling, spooling and output.
Thinkers slice the field differently. Peter Checkland and Brian Wilson separated technical hard systems from soft systems full of people and organisations, while George Klir argued that no classification suits every purpose. Library shelving under Dewey Decimal, Roman numerals and Boolean logic all qualify as systems too, since each links parts so information can flow.
Source: System
