IPO model

Many introductory programming and systems analysis texts introduce this as the most basic structure for describing a process.

[1] In essence the system separates itself from the environment, thus defining both inputs and outputs as one united mechanism.

Various analysts often set their own boundaries, favoring their point of view, thus creating much confusion.

[4] One of such definitions would outline the Input-process-output system, as a structure, would be: "Systems thinking is the art and science of making reliable inferences about behaviour by developing an increasingly deep understanding of the understanding of the underlying structure"[7] Alternatively, it was also suggested that systems are not 'holistic' in the sense of bonding with remote objects (for example: trying to connect a crab, ozone layer and capital life cycle together).

Examples of such would be mathematical and philosophical systems, which have been created by human minds, for some specific purpose.