Difference Between Coupling and Cohesion
In software engineering, Cohesion and Coupling are two important terminologies representing interconnection between different system parts. Most of us think both terms are the same, but it’s not the case. There are a lot of differences between coupling and cohesion.
Are you aware of the difference between coupling and cohesion? If not, then don’t worry. In this article, we will discuss the difference between these terms (Coupling and Cohesion) in detail.
The main difference between coupling and cohesion is that coupling refers to the degree of interdependence between modules or components in a software system. In contrast, cohesion refers to the degree to which elements within a single module or component work together to achieve a single purpose.
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Before exploring the difference between coupling and cohesion in-depth, let’s go through the topics listed under the table of contents (TOC) we will cover in this article. Here’s the table of contents:
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Difference Between Coupling and Cohesion
For a better understanding, let’s cover the difference between coupling and cohesion in a tabular format.
| Benchmark | Coupling | Cohesion |
|---|---|---|
| What is it? | It refers to the degree of interdependence between modules or components in a software system. | It refers to the degree to which elements within a single module or component work together to achieve a single purpose. |
| Also known as | Inter-module Binding | Intra-module Binding |
| It represents | The relationships between modules or components. | The relationship within a module or a component. |
| Created | Between two different modules. | Between the same module. |
| The best software is produced when there is | Loose coupling | High cohesion |
| An increase in | Coupling is avoided for software. | Cohesion is good for software. |
What is Coupling?
Coupling refers to the degree of interdependence between modules or components in a software system.
The high coupling means a module or component is highly dependent on others, while low coupling means it is more independent. The goal is to have low coupling, which allows for greater flexibility and maintainability in the software system. In layman’s terms, coupling represents the relationships between modules or components.
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There are six types of coupling. Let’s explore each of them.
| Coupling Type | Description |
|---|---|
| Common coupling | This type of coupling occurs when two or more modules share the same global data. |
| External coupling | This type of coupling occurs when a software module interacts with elements outside of its control and can change independently, such as other software systems, user interfaces, etc. |
| Control coupling | This type of coupling occurs when one module controls the execution of another. |
| Stamp coupling | This type of coupling occurs when a module requires a specific implementation of another module. |
| Data coupling | This type of coupling occurs when modules share data through parameters or return values. |
| Content coupling | This type of coupling occurs when a module directly accesses the data of another module. |
What is Cohesion?
Cohesion refers to the degree to which elements within a single module or component work together to achieve a single purpose.
High cohesion means elements are tightly related and work together to achieve a specific goal. Whereas low cohesion means elements are loosely related and do not have a clear purpose. The goal is high cohesion, leading to more modular and maintainable software systems. In layman’s terms, cohesion represents the relationship within a module or a component.
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There are six types of cohesion. Let’s explore each of them.
| Cohesion Type | Description |
|---|---|
| Functional cohesion | This type of cohesion occurs when all elements within a module are related to a single, well-defined function. |
| Procedural cohesion | This type of cohesion occurs when elements within a module are organized as a series of steps to achieve a function. |
| Temporal cohesion | This type of cohesion occurs when elements within a module are related by the time they are executed. |
| Sequential cohesion | This type of cohesion occurs when elements within a module are organized in a specific sequence to achieve a function. |
| Layer cohesion | This type of cohesion occurs when all the elements within a single layer are related to a single purpose and work together to achieve that purpose. |
| Communication cohesion | This type of cohesion occurs when elements within a module are related by the data they manipulate. |
Key Differences Between Coupling and Cohesion
Here are the key differences between coupling and cohesion:
- Coupling is also known as “Inter-module Binding.” In contrast, cohesion is known as “Intra-module Binding.”
- An increase in coupling is avoided for software. At the same time, an increase in cohesion is good for software.
- Cohesion is created between the same module. In comparison, the coupling is created between two different modules.
- The best software is produced when there is loose coupling. In contrast, high cohesion is required to produce the best software.
- Coupling represents the relationships between modules or components. But, cohesion represents the relationship within a module or a component.
- During cohesion, the goal is high cohesion, leading to more modular and maintainable software systems. But, while coupling, the goal is to have low coupling, which allows for greater flexibility and maintainability in the software system.
- Coupling refers to the degree of interdependence between modules or components in a software system. Whereas cohesion refers to the degree to which elements within a single module or component work together to achieve a single purpose.
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Conclusion
In simple terms, we can say that the main difference between coupling and cohesion is that coupling is about how much one component depends on others. Whereas, cohesion is about how well the elements within one component work together.
FAQs
How can high coupling and low cohesion impact software maintenance?
High coupling between modules makes it difficult to make changes or updates to one module without affecting other modules. Low cohesion within a module means its responsibilities are not well-organized, making it harder to understand and modify. Together, high coupling and low cohesion can significantly increase the effort and cost of software maintenance.
What design principles or patterns can help achieve loose coupling and high cohesion?
Some principles and patterns that promote loose coupling and high cohesion include the Single Responsibility Principle (SRP), the Interface Segregation Principle (ISP), the Dependency Inversion Principle (DIP), and the use of design patterns like Facade, Observer, and Strategy patterns.
How do coupling and cohesion relate to software quality attributes like reusability and testability?
Loosely coupled modules with high cohesion are more likely to be reusable, as they are independent and focused on a single responsibility. They are also easier to test in isolation due to their well-defined interfaces and limited dependencies.
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