The waterfall methodology is one of the software process models. It is believed to be the very first of its kind that was introduced and it is followed by a lot of software engineering practitioners. In the 1970s when programs were a lot simpler, such software process models were not necessary because programmers could still keep an abstract of the program that they are creating in their mind and then transfer it into code. As programs became bigger and more complicated throughout the years though, the requirements became bigger as well and programmers cannot operate in the same way that they used to. Hence, the waterfall methodology was created so that software development was broken down into several phases and simply cascaded in each other as one phase is finished. This also allows for the program to be checked after the whole process is complete.

In the simplified version of the waterfall methodology according to Sommerville, there are 5 steps that are necessary. First are the requirements, followed by the system design based on requirements. The third is the implementation of design. The fourth is the integration and system testing and last is the operation and maintenance. Let us discuss the 5 simplified steps one by one.

The requirement analysis and definition phase entails pointing out everything that is needed for the program to be set up. Requirements are collected by finding out what the needs of the end users are. The whole point of this phase is to come up with a requirements specification document, which is vital for the next phase of the waterfall methodology.

The second phase of the waterfall methodology is when the design portion of the project occurs. This entails designing both the software and the hardware. The full system architecture is drawn in this phase of the process.

One thing that you must know about programs is that it is completed in units and tested accordingly. At this stage of the waterfall methodology, the design process is done for the purpose of the development of the project requirements that were identified in the first stage

In the fourth phase, which is the integration and system testing phase, the tasks that each unit performed in the third stage are integrated until it produces one complete system. After which, it will be tested not as a unit but as a complete system in order to determine if it is deliverable to the client. Does the program work? This is the time when the programmers will be able to answer that question.

The final stage of the simplified waterfall methodology is the operation and maintenance stage. This phase usually takes longer than the four phases before it because this is when the system is tested for practical purposes. Here, all the problems that will arise during the operation testing will be resolved. If necessary, the system will be aligned with newer requirements should such requirements be pointed out.

In a nutshell, that is how the waterfall methodology works.