Explain the Waterfall model of the SDLC.

The Waterfall model is a linear and sequential approach to software development that follows a systematic and structured process. It consists of several distinct phases, including requirements gathering, system design, implementation, testing, deployment, and maintenance.

In the Waterfall model, each phase is completed before moving on to the next one, and there is little to no overlap between the phases. This means that the project progresses in a step-by-step manner, with each phase building upon the previous one.

The key characteristics of the Waterfall model include:

1. Requirements gathering: In this phase, the project requirements are identified and documented in detail. This involves understanding the needs of the stakeholders and defining the scope of the project.

2. System design: Once the requirements are gathered, the system design phase begins. This involves creating a detailed design of the software system, including its architecture, modules, and interfaces.

3. Implementation: In this phase, the actual coding and development of the software system takes place. The design specifications are translated into executable code using programming languages and development tools.

4. Testing: After the implementation phase, the software is thoroughly tested to ensure that it meets the specified requirements and functions correctly. This includes unit testing, integration testing, system testing, and user acceptance testing.

5. Deployment: Once the software has been tested and approved, it is deployed or released to the end-users or customers. This involves installing the software on the target environment and making it available for use.

6. Maintenance: After deployment, the software enters the maintenance phase, where any issues or bugs discovered during usage are addressed and fixed. This phase also includes regular updates and enhancements to improve the software's functionality and performance.

The Waterfall model is often used for projects with well-defined and stable requirements, where changes are expected to be minimal. It provides a clear and structured approach to software development, but it can be inflexible and less adaptable to changing requirements compared to other models like Agile.