Coupling vs. Cohesion — What's the Difference?
By Urooj Arif & Fiza Rafique — Updated on May 7, 2024
Coupling refers to the degree of interdependence between software modules, while cohesion describes how closely related and focused the responsibilities of a single module are.
Difference Between Coupling and Cohesion
Table of Contents
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Key Differences
Coupling in software development involves the degree to which different modules or components depend on each other. Lower coupling is generally preferred as it indicates that modules operate independently, which simplifies changes and maintenance. On the other hand, cohesion refers to how closely the tasks performed by a single module are related to each other, with high cohesion being ideal as it means a module handles only tasks closely related to its specific function.
When designing software, aiming for low coupling ensures that changing one part of the software doesn’t necessitate changes in others, thereby reducing the risk of introducing bugs during modifications. Conversely, high cohesion within a module makes it easier to understand and maintain because its functionality is clearly defined and isolated from unrelated functionalities.
Modules with low coupling are easier to test since their functions are less dependent on other parts of the system. Whereas, modules with high cohesion are beneficial because they encapsulate all relevant tasks, making them both robust and reusable without undue reliance on other modules.
In practice, developers strive to reduce coupling by minimizing the interactions between modules to just necessary communication, thereby promoting modular independence. Meanwhile, enhancing cohesion by grouping related functionalities within the same module supports better organization and clearer program structure.
The interaction between coupling and cohesion often dictates the overall quality and maintainability of software systems. Systems designed with low coupling and high cohesion are easier to manage, adapt, and scale compared to systems with high coupling and low cohesion, which can become complex and brittle over time.
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Comparison Chart
Definition
Degree of interdependence among modules
Degree of relatedness within a module
Desired Level
Low (less interdependence)
High (strongly related functionalities)
Impact on Testing
Easier to test individual modules
Facilitates comprehensive module tests
Impact on Changes
Changes in one module affect fewer others
Changes are confined within the module
Relationship to Quality
Lower coupling enhances maintainability
Higher cohesion increases clarity and utility
Compare with Definitions
Coupling
The reliance of modules on each other's functionality.
Loose coupling is a key principle in modular programming.
Cohesion
The internal consistency of a module.
They evaluated the module's cohesion to identify potential improvements.
Coupling
The interconnection between different software components.
High coupling made it difficult to modify the legacy code.
Cohesion
A measure of how closely related and focused the tasks within a module are.
Increasing cohesion made the module more self-contained.
Coupling
Dependency between different parts of a program.
They implemented an interface to decrease the coupling.
Cohesion
The concentration of a module's responsibilities.
Good cohesion helps keep the module's functionality understandable.
Coupling
The link between software units.
We used a mediator pattern to manage the coupling between components.
Cohesion
Unity within a software module.
High cohesion ensures that module functions are closely aligned with its purpose.
Coupling
A measure of how much one module relies on another.
Reducing coupling was essential for simplifying the system upgrade.
Cohesion
The degree to which elements of a module belong together.
The team improved the module's cohesion by refactoring.
Coupling
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both.
Cohesion
The act, process, or condition of cohering
Exhibited strong cohesion in the family unit.
Coupling
The act of linking together or forming couples.
Cohesion
(Physics) The intermolecular attraction by which the elements of a body are held together.
Coupling
A device that links or connects.
Cohesion
(Botany) The congenital union of parts of the same kind, such as a calyx of five united sepals.
Coupling
(Electronics) The transfer of electricity from one circuit to another.
Cohesion
State of cohering, or of working together.
Unit cohesion is important in the military.
Coupling
(Chemistry) Facilitation or acceleration of one chemical process due to the presence or action of another.
Cohesion
Various intermolecular forces that hold solids and liquids together.
Coupling
The body part of a four-footed animal that connects the hindquarters to the forequarters.
Cohesion
(biology) Growing together of normally distinct parts of a plant.
Coupling
Act of joining together to form a couple.
Cohesion
(software engineering) Degree to which functionally related elements in a system belong together.
Coupling
A device that couples two things together.
Cohesion
(linguistics) Grammatical or lexical relationship between different parts of the same text.
Coupling
(software engineering) The degree of reliance between two or more software modules.
Cohesion
The act or state of sticking together; close union.
Coupling
(electronics) A connection between two electronic circuits such that a signal can pass between them.
Cohesion
That from of attraction by which the particles of a body are united throughout the mass, whether like or unlike; - distinguished from adhesion, which unites bodies by their adjacent surfaces.
Solids and fluids differ in the degree of cohesion, which, being increased, turns a fluid into a solid.
Coupling
(physics) The property of physical systems that they are interacting with each other
Cohesion
Logical agreement and dependence; as, the cohesion of ideas.
Coupling
Present participle of couple
Cohesion
The state of cohering or sticking together
Coupling
A device or contrivance which serves to couple or connect adjacent parts or objects; as, a belt coupling, which connects the ends of a belt; a car coupling, which connects the cars in a train; a shaft coupling, which connects the ends of shafts.
Cohesion
(botany) the process in some plants of parts growing together that are usually separate (such as petals)
Coupling
A connection (like a clamp or vise) between two things so they move together
Cohesion
(physics) the intermolecular force that holds together the molecules in a solid or liquid
Coupling
A mechanical device that serves to connect the ends of adjacent objects
Coupling
The act of pairing a male and female for reproductive purposes;
The casual couplings of adolescents
The mating of some species occurs only in the spring
Common Curiosities
Can a system have low coupling and low cohesion?
Yes, but such a system would likely be poorly designed, hard to maintain, and difficult to understand.
What is coupling in software development?
Coupling refers to how much modules depend on each other in a system.
Why is high cohesion desirable in a module?
High cohesion means that a module’s functionalities are closely related, enhancing understandability and maintenance.
How do developers achieve low coupling?
Through careful design that minimizes the direct dependencies between different modules, often using patterns like facade or mediator.
What design pattern can help reduce coupling?
The mediator pattern is frequently used to decrease coupling by centralizing complex communications between components.
How do cohesion and coupling affect scalability?
Systems with low coupling and high cohesion are generally more scalable, allowing for easier expansion and modification.
What are the consequences of high coupling?
High coupling can lead to a fragile system where changes in one module ripple through others, potentially causing bugs.
How does low coupling affect system maintainability?
Low coupling makes it easier to modify, test, and understand separate modules, thereby enhancing maintainability.
Is it possible to have zero coupling?
In practical applications, zero coupling is nearly impossible but minimizing coupling is a common and beneficial goal.
Does high cohesion limit the flexibility of a module?
On the contrary, it tends to increase module flexibility by keeping all related functionalities together, making them easier to update.
What testing advantages does low coupling provide?
It allows for more isolated and therefore simpler testing scenarios for each module.
What is an example of a change that affects a highly cohesive module?
Changes within a highly cohesive module typically remain confined to that module, affecting only closely related functionalities.
What role does interface play in managing coupling?
Interfaces can decouple the implementation details of modules from their usage, reducing the direct dependencies.
Can high cohesion lead to oversized modules?
While possible, high cohesion should not compromise the module’s manageability and should focus on related functionalities only.
How do changes in technology impact coupling and cohesion?
Advances in technology and methodology, like microservices architecture, often promote lower coupling and higher cohesion, leading to more robust and maintainable systems.
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Written by
Urooj ArifUrooj is a skilled content writer at Ask Difference, known for her exceptional ability to simplify complex topics into engaging and informative content. With a passion for research and a flair for clear, concise writing, she consistently delivers articles that resonate with our diverse audience.
Co-written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
