Principles and Types of a System

There are 5 major principles that guide good system design.

1. Principle of Decomposition: This principle deals with being able to break down an information system into various components. The components of sub-system are further broken down into smaller sub-system depending on their functions. The idea is to decompose a complex system in successive layers of the main system is decomposed into successive sub-systems until the lowest level of sub-systems is of manageable complexity.
2. Principle of Simplification: This principle signifies the inter-connection between system components and a mathematical formula is used to identify such interconnections. This principle is the process of organising sub-systems so as to reduce the number of interfaces between system components if there are n sub-systems then interfaces will be determined by the formula-   n(n-1)/2
3. Principle of modularity: This principle divides the system into modules of uniform sub-systems. These modules can represent an information system simply making it not only understandable but also easier to be built.
4. Principle of coupling: Coupling is extent to which system components are dependent to each other, it is the strength of interconnection between modulus for a measure of interdependence among sub-systems. It is a degree to which a component or module is connected to the other module. It is independent or inter module concept while designing a system we should strive for low coupling. Therefore dependency between the module will be less.
5. Principle of cohesion: It is the extent to which a module performs a single function. It is the indication of relationships within module. it represent how tightly bound the internal elements of a module to one another, it shows the models relative function strength. It is intra module interdependent concept while design assystem we should strive for high cohesion i.e. cohesive component focuses on a single task with little interaction with other modules of a system.

Types of system 

1.  Physical and Abstract system: Physical systems are tangible entities which we can feel and touch. For example- fan, monitor etc. Physical system could be static or dynamic. For example: steel cabinet is a static physical system whereas an air-condition is dynamic physical system which responds to the environment and changes with time. Abstract system all conceptual means they are based on concepts they may be formulas, representation or model of a system. These systems are used to understand the physical system, their components and their inter-relationships.
2. Probabilistic and deterministic system: Probabilistic system shows probable behaviour and acts in an unpredictable manner, hair the exact output is not known. There is always chances of degree of error in system. In deterministic system interaction among the components is known with certainty. Hence, occurrence of all the events at predictable or known. The stepwise execution is done and output is already known.
3. Permanent and temporary system: Permanent system persist for longer period of time whereas temporary system is made for some time and after that, they are dissolved.
4. Machine and natural system: The systems made by man are known as machine system also known as artificial system whereas systems agar in nature natural system. 
5. Open and closed system: An open system is defined as one that exchanges information material or energy with the environment. Biological systems and business organisation open system. Open system interacts with its environment by receiving inputs from and delivering outputs to outside environment and they possess permeable boundaries through which new ideas and information are absorbed. They can adapt more quickly according to changes in external environment through which day operate. As the environment influences the system also influences an environment. An open system regularly exchanges the feedback with its external environment, analyse the feedback and adjust the internal system to achieve system goal.

Characteristics of Open and Closed System

1. Inputs from outside: Open systems are self-adjusting and self-regulated and function properly. An open system reaches a steady state called equilibrium.
2. Entropy: The system tendency is to lose energy over time open systems resist entropy by seeking new inputs or modifying the process to return a steady state.
3. Equifinality: It means that same or similar results can be achieved by using variety of different processes.
4. Differentiation: Open system has a tendency towards and increasing speciality. The role of machine and people turned towards greater specialisation. Closed system is defined as one which does not interact with the environment it resist incorporating new ideas and cannot adapt according to the environment such systems are subject to increase in entropy and disorder. For e.g. chemical reaction in a sealed isolated container.