Software Engineering basics - Classical Waterfall Model
Classical Waterfall Model in Software Engineering
The Classical Waterfall Model is one of the earliest and most straightforward software development life cycle (SDLC) models. It follows a linear, sequential flow, meaning each phase must be completed before moving to the next—like water flowing down a waterfall.
Definition:
The Waterfall Model is a structured software development approach where the process flows in a step-by-step manner from requirements to maintenance, with no overlap between phases.
Phases of the Classical Waterfall Model
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1. Requirements Gathering & Analysis
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Understand what the customer wants.
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All functional and non-functional requirements are collected and documented.
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Output: Software Requirement Specification (SRS)
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2. System Design
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Based on requirements, the overall system architecture and design are created.
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Output: System Design Documents (architecture, data models)
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3. Implementation (Coding)
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Actual coding starts.
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Developers write the code based on the system design.
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Output: Working source code
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4. Testing
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Software is tested to ensure that it meets the specified requirements.
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Bugs and defects are reported and fixed.
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Output: Tested and verified product
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5. Deployment
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Software is deployed in the user’s environment.
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May include installation, setup, and training.
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6. Maintenance
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Fixing bugs or issues that come up after deployment.
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Includes updates and enhancements over time.
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Visual Diagram of Waterfall Flow
Requirements → Design → Implementation → Testing → Deployment → Maintenance
Each phase flows downward to the next, with little to no feedback loop.
When to Use the Waterfall Model
Best suited for:
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Projects with clearly defined requirements
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Short-duration projects
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Projects where no expected changes will occur during development
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Government or military software projects (where strict documentation is needed)
