🧠What is Software Design?
Software Design is the process of defining the architecture, components, interfaces, and logic for a software application based on the specified requirements.
But how do we know if a design is good or bad?
A good software design is one that makes the software reliable, maintainable, scalable, and efficient.
âś… Characteristics of a Good Software Design
Here are the 10 most important characteristics of good software design, explained with examples:
1. Modularity
Divide and conquer!
Definition: The system is divided into small, manageable modules, where each module performs a specific function.
Benefits:
- Easy to understand and debug
- Enhances code reusability
- Parallel development possible
Example:
In an e-commerce website, separate modules for:
- Login
- Product catalog
- Cart
- Payment gateway
2. Cohesion
A module should do one thing only — and do it well!
Definition: Cohesion refers to how closely related the functions within a module are.
Types:
- High Cohesion (best): All functions are focused on one task.
- Low Cohesion (bad): Functions are unrelated.
Example:
A LoginModule should only handle login activities — not display product info.
3. Low Coupling
Keep modules independent!
Definition: Coupling refers to how much one module depends on another.
Goal: Achieve low coupling, where modules interact as little as possible.
Example:
Changing the Payment module should not break the Cart module.
4. Abstraction
Hide the details, show only what’s necessary.
Definition: Showing only essential features and hiding internal details.
Benefits:
- Better security
- Easier to understand
- Prevents misuse
Example:
User interacts with a “Place Order” button but doesn’t need to know the backend database logic.
5. Reusability
Don’t reinvent the wheel.
Definition: A good design allows code components to be reused in multiple applications.
Example:
A validateEmail() function can be reused in registration, login, and contact forms.
6. Scalability
Can your system grow?
Definition: Ability of software to handle more data, users, or features without major changes.
Example:
A chat app that works well with 10 users should still work smoothly when scaled to 10,000 users.
7. Maintainability
Easy to fix, update, and improve!
Definition: Software should be easy to modify when bugs are found or new features are added.
Factors that help maintainability:
- Clean code
- Comments
- Modularity
Example:
If the tax rules change, a well-designed system allows you to update just one module.
8. Performance and Efficiency
Fast and resource-friendly.
Definition: Software should make optimal use of system resources like memory, CPU, and network.
Example:
A good design fetches only 10 records per page instead of loading all 10,000 records at once.
9. Security
Protect your data and system.
Definition: Software must be designed to prevent unauthorized access, data leaks, and misuse.
Techniques:
- Encryption
- Authentication
- Secure coding practices
Example:
Password fields should store values in encrypted form.
10. Consistency and Simplicity
Simple is powerful!
Definition: The design should follow consistent naming, layout, and logic across modules.
Benefits:
- Easier for developers to understand and collaborate
- Reduces confusion and errors
Example:
If one module uses camelCase, all others should too. If one screen shows “Submit”, don’t call it “Send” elsewhere.
đź“‹ Summary Table
| Characteristic | Description | Goal |
|---|---|---|
| Modularity | Break system into small parts | Manageability |
| Cohesion | One task per module | Simplicity & clarity |
| Coupling | Low interdependence between modules | Flexibility |
| Abstraction | Hide internal details | Simplicity, security |
| Reusability | Code usable in multiple places | Saves time and effort |
| Scalability | System can grow with time | Long-term usefulness |
| Maintainability | Easy to update and fix | Reduce development cost |
| Efficiency | Uses fewer resources | Performance |
| Security | Prevent unauthorized access | Data protection |
| Consistency | Uniform design standards | Usability & collaboration |
🧠Viva Questions
- What is the difference between cohesion and coupling?
- Why is modularity important in software design?
- Give an example of abstraction in software systems.
- How does maintainability benefit the client?
- Name two characteristics that improve software security.