Software Design
Software Design: Simplified for Students
What is Software Design?
Software design is the process of converting requirements into a structured plan for building the software. It defines how the system will function internally, focusing on architecture, data structures, and algorithms.
Objectives of Software Design
- Correctness – Must meet all specified requirements
- Efficiency – Optimal resource usage
- Understandability – Easy to read and modify
- Modularity – Break down system into modules
- Maintainability – Easy to fix bugs and extend
- Reusability – Components usable in other systems
Levels of Design
- Architectural Design: High-level structure of the system
- Detailed Design: Internal logic of modules
- Interface Design: How components and users interact
Core Design Principles
- Modularity: Divide into independent parts
- Abstraction: Show only essential details
- Encapsulation: Hide internal workings
- Separation of Concerns: Single responsibility per module
- Low Coupling & High Cohesion: Ideal module interaction and responsibility
- Design for Change & Testability: Easy updates and effective testing
Design Tools and Notations
- UML: Class, Use-case, Sequence, Activity diagrams
- DFD: Shows data flow between components
- ER Diagram: Database relationships
Structured vs Object-Oriented Design
| Aspect | Structured Design | Object-Oriented Design |
|---|---|---|
| Focus | Functions and procedures | Objects and classes |
| Data & Function | Separate | Combined in objects |
| Reusability | Low | High |
| Maintenance | Difficult | Easy |
| Examples | C | Java, Python, C++ |
Architectural Styles
- Layered: UI → Logic → Data layers
- Client-Server: Client requests, server responds
- Pipe and Filter: Data processed in stages
- Event-Driven: Based on events and responses
Component-Based Design
This approach uses reusable, independent software components. It enables faster development and easier maintenance through well-defined interfaces.
User Interface (UI) Design
- Simple: Easy to use
- Consistent: Uniform layout and navigation
- Responsive: Provides feedback
- Accessible: Inclusive for all users
Design Documentation
- UML and DFD diagrams
- Module descriptions
- Interfaces between components
- Data dictionaries and logic notes
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