What is Coupling - peak concepts

Coupling: Two modules are considered independent if one can function completely without the presence of other. Obviously, if two modules are independent, they are solvable and modifiable separately. However, all the modules in a system cannot be independent of each other, as they must interact so that together they produce the desired external behavior of the system. 

The more connections between modules, the more dependent they are in the sense that more knowledge about one module is required to understand or solve the other module. Hence, the fewer and simpler the connections between modules, the easier it is to understand one without understanding the other. Coupling between modules is the strength of interconnection between modules or a measure of independence among modules.

 

To solve and modify a module separately, we would like the module to be loosely coupled with other modules. The choice of modules decides the coupling between modules. Coupling is an abstract concept and is not easily quantifiable. So, no formulas can be given to determine the coupling between two modules. However, some major factors can be identified as influencing coupling between modules.

 

Among them the most important are the type of connection between modules, the complexity of the interface, and the type of information flow between modules. Coupling increase with the complexity and obscurity of the interface between modules. To keep coupling low we would like to minimize the number of interfaces per module and the complexity of each interface. An interface of a module is used to pass information to and from other modules. Complexity of the interface is another factor affecting coupling.

 

The more complex each interface is, higher will be the degree of coupling. The type of information flow along the interfaces is the third major factor-affecting coupling. There are two kinds of information that can flow along an interface: data or control, Passing or receiving control information means that the action of the module will depend on this control information, which makes it more difficult to understand the module and provide its abstraction. Transfer of data information means that a module passes as input some data to another module and gets in return some data as output.

 

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