The waterfall model is the traditional method used in the SDLC as it has a linear and sequential pattern to it. The development of the software moves from the top to the bottom, with each phase needing to be completed before the next phase can begin:
It starts with gathering information about the requirement, then it is put into the design phase, and then it is implemented. The testing phase is carried out before it goes into production; any testing carried out will be rolled back prior to deployment. The maintenance phase is for patching and fixing any bugs.