Iterative development process is more practical than the waterfall model. It does not assume that the customer gives all requirements in one go and there is complete stability of requirements. It assumes that changes may come from any phase of development to any previous phase and there are multiple permutations and combinations of changes. Changes may have a cascading effect where one change may initiate a chain reaction of changes. Figure 2.3 shows a feedback loop which is the fundamental difference between waterfall model and iterative development model.