Waterfall Model

Testers have very well known about these models-

Waterfall Model
V Model
Spiral Model
Agile Model
'W' Model
Butterfly Model

 Let we discuss about waterfall model, later on we will study about remaining models.
Waterfall model - is a step by step method for achieving the task. In this model one can go to the next phase only after the completion of current phase.
In this model each phase of activity is followed by the verification and validation activity. Every phase is
Completed with testing then going to the next phase of cycle. Here we can move immediate previous phase.
Like, here we take one example - We cannot go from testing phase to the design phase.