Coupling and cohesion are both important concepts in software design that describe how different parts of a software system are related to each other.
Coupling refers to the degree of interdependence between different modules or components of a software system. It is a measure of how much one component relies on another component in order to function properly. High coupling means that changes to one component will have a significant impact on other components, which can lead to maintenance difficulties and make the system less flexible. Low coupling, on the other hand, means that components are relatively independent and changes to one component will have minimal impact on other components.
Cohesion, on the other hand, refers to the degree to which the elements within a module or component are related to each other. It is a measure of how well a component or module performs a single, well-defined task. High cohesion means that the elements within a module are closely related and work together to achieve a common goal. Low cohesion means that the elements within a module are not closely related and do not work together in a coherent manner.
In summary, coupling describes the degree of interdependence between different components of a system, while cohesion describes the degree of relatedness between the elements within a single component. Ideally, a software system should have low coupling and high cohesion, as this makes it easier to maintain, modify, and extend the system over time.