Explain waterfall model and agile method, how do they differ.
Explain how agile addresses complexity and uncertainty

Waterfall model is a sequential software development process. Sequential means that the next step is undertaken after the previous step has been completed. Each stages involved, for instance conception, initiation, testing, and implementation, to mention a few must be completed before moving to the next steps.  As one step is completed, the software developers cannot go back to the step again. If this has to be done, then the whole project will have to be scratched and thus made to start from the first step. This model can be understood better by considering the manufacturing and construction processes. In this processes, strict various steps must be followed, (Yoder, 2015).