Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. An open system is a system which continuously interacts with its environment. The interaction 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 (see below). An open system should be contrasted with the concept of an isolated system which exchanges neither energy, matter, or information with its environment. The concept of an "open system" was formalized within the framework of thermodynamics. 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.