Systems have very specific common characteristics which help in its identification. They are:
- Systems have a specific structure which is defined by its components (entities/subsystems) and processes (interrelationships between its components). A system is a collection of interrelated entities and/or subsystems which can be analyzed. It is possible to understand the specific structure of a system. However, in some systems complete knowledge may not be available but in most cases the fundamental entities and their interrelations are known.
- Systems are a model of reality-a system is an abstraction of reality. It is created to comprehend the nuances of a real-world condition and understand the interrelationships of subsystems in such real-world conditions in greater clarity.
- A system has a purpose-a system performs a function. It has a reason for its existence. The purpose in most cases is the output of the system and in a way the output defines the purpose of the system.
- Systems have inputs and outputs. Outputs are produced by processing the inputs-a system (unless of theoretical interest and fully closed), interacts with the environment by taking in input and then after processing the input produces the output.
- Systems have performance that can be measured in terms of its output-a system will have measures of performance. In most cases, the performance of the system is a function of its input and output.
- A system serves a client-the system will have a utility and hence, a client for it. The client can also be another system.
- The components that make up a system have functional as well as structural interrelationships with each other.
- A system has an environment-a system cannot exist in isolation. It exists in an environment. The environment reacts with it.
- Each subsystem also has a purpose and a measure of purpose.