Control and exchange of information, also called communication , takes place in all systems. The term system covers both the system elements and their interactions. These generate the system properties . The theory covering the behaviour of systems is called system theory. Systems that live in a continuous exchange with their environment are called open systems .
All living systems are open and in a steady state .
This means that they are never in an stationary equilibrium. The system theory allows the description of system elements as 'black boxes' that are characterized by only their output and input. Such a system element is also called a transitional element . Every system has a certain capacity , too big input signals may consequently lead to damage or disruption of the system. Deterministic systems have elements that co-operate in a predictable way, probabilistic systems can never be fully understood and thus only be described in a probabilistic way.