Open Systems
An open system is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept. An open system is contrasted with the concept of an isolated system which exchanges neither energy, matter, nor information with its environment. An open system is also known as a flow system.
The concept of an open system was formalized within a framework that enabled one to interrelate the theory of the organism, thermodynamics, and evolutionary theory. This concept was expanded upon with the advent of information theory and subsequently systems theory. Today the concept has its applications in the natural and social sciences.
In the natural sciences an open system is one whose border is permeable to both energy and mass. By contrast, a closed system is permeable to energy but not to matter.
The definition of an open system assumes that there are supplies of energy that cannot be depleted; in practice, this energy is supplied from some source in the surrounding environment, which can be treated as infinite for the purposes of study. One type of open system is the radiant energy system, which receives its energy from solar radiation – an energy source that can be regarded as inexhaustible for all practical purposes.
(From Wikipedia)
In systems theory, an open system is a system that interacts with other systems by having inputs or outputs. A closed system is one that is totally self-contained and does not input or output anything.
As an example of an open system, consider the human body. It requires the inputs of food and oxygen to continue to function, and it outputs carbon dioxide and other waste, which must be handled by other systems. Earth, as a whole, can be considered a closed system, as nothing generally enters or leaves it except the energy from the sun.
(From https://www.techtarget.com/whatis/definition/open-system)
The concept of an open or closed system can also have value in business and software design. The inputs and outputs of a company or process can be analyzed. Software can be designed to be entirely self-reliant or to exchange data with external programs and sources.
An open system might also be fully transparent, or open to inspection by outsiders. For example, in an open government, all government documents are available to the public, and anyone can attend or view meetings of the legal bodies.
(From https://www.techtarget.com/whatis/definition/open-system)