📘 What is Software Design?
Software Design is the process of defining architecture, components, interfaces, and data for a software system to meet specified requirements.
✅ It acts as a blueprint for software construction — just like a building’s architectural plan!
🧱 Why is Software Design Important?
- Ensures clarity before coding
- Helps in modular, scalable, and maintainable software
- Reduces errors and cost in later phases
- Makes the development process more systematic
🛠️ Major Activities in Software Design
Software Design is carried out in two main phases:
1. 🏗️ High-Level Design (Architectural Design)
Also known as System Design, it focuses on the overall structure of the system.
Activities:
| Activity | Description |
|---|---|
| System Decomposition | Dividing the system into subsystems/modules |
| Interface Design | Defining how modules interact with each other |
| Data Design | Identifying data structures and database organization |
| Technology Selection | Deciding platforms, frameworks, or tools |
🔍 Example: Dividing an online food delivery system into modules like User Login, Menu Display, Order Management, Payment, and Delivery Tracking.
2. 🧩 Detailed Design (Low-Level Design)
This is where each module/component is designed in detail.
Activities:
| Activity | Description |
|---|---|
| Algorithm Design | Creating step-by-step logic for modules |
| Data Structure Design | Selecting appropriate data structures (arrays, trees, etc.) |
| Component Design | Describing functions, methods, inputs, and outputs |
| User Interface Design (UI) | Designing the layout and user interaction |
🔍 Example: Writing pseudocode or flowcharts for the “Order Management” module, showing how to add items, remove items, and calculate total price.
🔑 Design Principles to Follow
- Modularity: Break the system into independent modules
- Abstraction: Hide internal details and show only necessary features
- Reusability: Design components that can be reused in other projects
- Cohesion & Coupling:
- High Cohesion (each module does one job)
- Low Coupling (modules depend less on each other)
🧠 Simple Example – “Online Library System”
| Module | Design Consideration |
|---|---|
| User Login | Interface with username/password check |
| Book Search | Algorithm for filtering by name, author, genre |
| Borrow Book | Data flow between user account and book inventory |
| Admin Panel | Separate interface for adding/removing books |
📋 Summary
| Term | Definition |
|---|---|
| Software Design | The process of planning a software solution’s structure |
| High-Level Design | Focuses on modules, interfaces, and data flow |
| Low-Level Design | Focuses on algorithms, functions, and logic |
| Design Principles | Modularity, Abstraction, Reusability, Cohesion & Coupling |
🧠 Viva Questions
- Q: What is the difference between high-level and low-level design?
A: High-level design focuses on system structure; low-level design focuses on module internals. - Q: What is modularity in software design?
A: Dividing software into independent, manageable modules. - Q: Give one example of design activity in software engineering.
A: Algorithm design in the detailed design phase.