The types of coupling in software engineering describe the degree of interdependence between software modules. Lower coupling indicates better software design. Here's a breakdown of the common coupling types:
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Content Coupling: This is the worst type of coupling, occurring when one module directly modifies or depends on the internal workings of another module (e.g., directly accessing or modifying local data of another module). It's highly undesirable and makes maintenance and reuse extremely difficult.
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Common Coupling: This occurs when multiple modules access the same global data. Changes to the global data can inadvertently affect all modules that use it, making it difficult to track down the source of errors.
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Control Coupling: In control coupling, one module controls the logic flow of another module. This often involves passing control flags or modifying the state of the called module in a way that dictates its behavior.
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Stamp Coupling (Data-Structured Coupling): Stamp coupling happens when modules share a composite data structure (e.g., a record or object), but the called module only uses a part of the structure. While not as bad as content or common coupling, it can still lead to unnecessary dependencies and decreased modularity.
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Data Coupling: This is the best type of coupling. It occurs when modules share data through parameters or arguments, and only the necessary data is passed. This promotes modularity and reduces the risk of unintended side effects.
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External Coupling: External coupling arises when modules depend on an external element like a protocol, external device, or file format.
In summary, the goal of good software design is to minimize coupling as much as possible to create more maintainable, reusable, and understandable software.
