SDLC - Waterfall Model

This is the most common and classic of life cycle models, also referred to as a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed in its entirety before the next phase can begin. At the end of each phase, a review takes place to determine if the project is on the right path and whether or not to continue or discard the project. Unlike what I mentioned in the general model, phases do not overlap in a waterfall model.

Waterfall Life Cycle Model Diagram


Advantages
Simple and easy to use.
Easy to manage due to the rigidity of the model – each phase has specific deliverables and a review process.
Phases are processed and completed one at a time.
Works well for smaller projects where requirements are very well understood.
Disadvantages
Adjusting scope during the life cycle can kill a project
No working software is produced until late during the life cycle.
High amounts of risk and uncertainty.
Poor model for complex and object-oriented projects.
Poor model for long and ongoing projects.
Poor model where requirements are at a moderate to high risk of changing.