what is a system
A system is a general set of parts, steps, or components that are connected to form a more complex whole. For example, a computer system contains processors, memory, electrical pathways, a power supply, etc. For a very different example, a business is a system made up of methods, procedures, and routines.
Systems theory. Systems theory or systems science is the interdisciplinary study of systems. A system is an entity with interrelated and interdependent parts; it is defined by its boundaries and it is more than the sum of its parts (subsystem). Change in one part of the system affects other parts and the whole system, with predictable patterns of behavior.