The Waterfall Model is a traditional software development methodology that follows a linear and sequential approach. It was first introduced by Winston W. Royce in 1970 and is one of the earliest SDLC models used in software engineering¹. The model is named "waterfall" because the development process flows downwards through several phases, similar to a waterfall².

Key Principles

The Waterfall Model consists of distinct phases that must be completed in a specific order. Each phase serves as a foundation for the next, and there is no overlapping between phases². The main phases are:

1. Requirements Gathering and Analysis: This phase involves collecting all possible requirements of the system from stakeholders and documenting them in a requirement specification document².

2. System Design: Based on the requirements, the system design is prepared, specifying hardware and system requirements and defining the overall system architecture².

3. Implementation: The system is developed in small units, which are integrated in the next phase. Each unit is developed and tested for functionality².

4. Integration and Testing: All units are integrated into a system, and the entire system is tested for any faults and failures².

5. Deployment: The product is deployed in the customer environment or released into the market².

6. Maintenance: Patches are released to fix issues, and better versions are released to enhance the product².