Waterfall model 16 is the Sequential development model. ? Requirement should be clear before going to next phase of design. ? Testing is carried out once the code has been fully developed. Each work-product or activity is completed before moving on to next ? Each phase of development proceeds in order without any overlapping. ? Each phase schedule for the tasks to be completed within a specified time period ? The documentation and testing happens at the end of each phase, which helps in maintaining the quality of the project. ? In the waterfall model each step is frozen before the next step. That is the requirements are frozen before the design starts, and once the design is frozen the coding starts etc. But what will the testing team do till then so is very time consuming and high costing ? In waterfall model the defect were found very late in the development life cycle as test team was not involved from the beginning of the project. ? Tester role will be involved in testing phase only Figure 1: Waterfall Model Life Cycle Requirement given by the client should be clear before we start the next phase of development life cycle because in waterfall model the requirement phase should be freeze before we start the design phase. Further changes in requirement will not be considered. 3.1.1 Pros ? Requirement is clear before development starts. ? Each phase is completed in specified period of time after that it moves to next phase. ? As its linear model, it’s easy to implement. ? The amount of resources required to implement this model are minimal. ? Each phase proper documentation is followed for the quality of the development. 3.1.2 Cons ? The problems with one phase are never solved completely during that phase and in fact many problems regarding a particular phase arise after the phase is signed off, this result in badly structured system. ? If client want the requirement to be changed , it will not implemented in the current development process In spite of the cons, the many pros of this model ensure that it remains one of the most popular models used in the field of software development.