The waterfall model is a classical model used in system development life cycle to create a system with a linear and sequential approach. It is termed as waterfall because the model develops systematically from one phase to another in a downward fashion. This model is divided into different phases and the output of one phase is used as the input of the next phase. Every phase has to be completed before the next phase starts and there is no overlapping of the phases.
The sequential phases described in the Waterfall model are:
1. Requirement Gathering
2. Analysis Read
3. System Design
5. Integration and Testing