Introduction

One of the earliest debates in software engineering is between the waterfall and V models. It can be hard for software developers to select between these two approaches because each has benefits and drawbacks. A software development process goes through several stages. The waterfall and V models are the two that are used most frequently in software development. They are among the oldest models used in software development. Whether it's the waterfall model or the V model, there will surely be many people who prefer one over the other.

V Model

It's often said that the V model is an extension of the waterfall model. In contrast to the waterfall model, the processes in this approach vent into a 'V' form, with coding at the bottom tip of the "V". The testing cycle corresponds to each component of the software development cycle. As a result, this model tends to be referred as the verification and validation model. Development is on the verification side, while testing is done on the validation side. The following activities are included on the verification side:

Requirement analysis: Information regarding the proposed system is obtained from the end user and used to generate a document that acts as the basis for the created software.
System Design: Also referred to as functional design, this process develops the software's functional design. The user gets informed if there is any capability that is not possible.
Architecture Design: After the system design has been finished, the architecture, also known as high-level design, is created for the system. Here, work is done on the interface relationship, tables in the database, their dependencies, etc.
Coding: The coding stage begins after the system architecture has been created. The complete system is divided into smaller components for development, which are then combined to create the entire system.

The validation part of the V model follows the verification side. Let's discuss the stages that comprise the validation side.

Unit testing is the first stage in the validation process, during which, generated small modules are tested to see if they serve their intended purpose.
Integration testing: It is done after the components are combined and complete. It helps in identifying interface and module-to-module interactions and errors.
System testing: The system testing phase involves carrying out the system test plans that were created in the system design phase and are put together by the client's business team. System testing guarantees the team meets the requirements of the application developer.
User Acceptance Testing: This testing aims to determine whether the system meets the definition of software requirements. It assists in determining if the system should be accepted and whether the generated software complies with the acceptance criteria. Furthermore, this testing phase is conducted in a real-time simulation.

Waterfall Model

The waterfall model is the most traditional one used in software development. It originated in the industrial and construction sectors. Since there was no model then, it was embraced in software development. Winston W. Royce created the official description of this concept but did not refer to it as a waterfall model. This paradigm follows a sequential flow, with each stage progressing like a chain reaction. The waterfall model has the following different stages:

Requirement Gathering and Analysis: The client's requirements are gathered and analyzed during this phase. Using the results of this analysis, a document describing the requirements is then developed. The basis for creating the system is this document.
Design: every component of the software is created during this essential phase, taking the software requirements into view. The requisite software and hardware specifications are developed along with the system architecture.
Implementation: The software's code is written during the implementation stage, which follows the design stage. Unit tests are performed on the modules once they are complete, which helps to identify any software issues. All coding mistakes must be fixed before moving on to the next level.
Testing and debugging: After being fully completed, the software is sent to the testers. Several tests are performed on the software, and issues are fixed.
Delivery: Following debugging, the software is implemented on the client side once it has been sent. The client gets extensive knowledge of the software so he can use it.
Maintenance: After the client has used the product for a while and requested adjustments, maintenance is required. During this stage, the software is modified and generally maintained.

Differences between waterfall Model and V Model

Waterfall Model	V Model
1.Every stage of the waterfall model must be finished before the next one can start because it is sequential in nature. There is no chance to go back and complete a task at a previous stage.	1.The V Model enables the programmer to inspect and modify things if something is inaccurate or may be improved, unlike waterfall models, where each stage must be completed before moving on to the next. The programmer has the choice to modify the software as necessary after each cycle (stage).
2. The software goes through several stages of development in the waterfall model. Since each step is finished before the next one starts, there are no deliverables.	2. Every step (cycle) of development has deliverables in the V model. Since things can change depending on requirements, there are no deliverables at the final stage of each phase.
3. Requirements are collected from numerous sources and then analysed using a variety of techniques. After collection and analysis, the requirements can be used for development.	3. Similar to the V Model, needs are obtained from many sources like interviews, surveys, etc. and examined using a variety of techniques such as brainstorming, data flow diagrams, etc. The development of the software can begin after the requirements are complete. The V model and the waterfall model differ greatly in this regard.
4. Returning to the earlier step is not allowed in the waterfall model. The next task starts when the previous one is completed.	4. In contrast to waterfall models, which make it impossible to review earlier stages, the V model enables programmers to do so..
5. The waterfall model's stages or phases are entirely independent of one another. It is more constrained than V models since each stage has only one entry and exit point, as opposed to V models' four entry and exit points.	5. The V model is cyclical in nature as opposed to the waterfall model, which has all stages that are independent of one another and just one entry and exit point. Four entry and exit points are present in each stage or phase. Because of this, the V paradigm is not only more adaptable than the waterfall model but also more flexible than every other software development paradigm.
6. In order to construct the software, the waterfall model fails to conform to a predetermined definition or procedure.	6. In contrast to waterfall models, where it is impossible to specify a predetermined process or procedure, V models need to be composed of a variety of definitions and procedures.
7. Testing a software component or programme as it is being developed is impossible with waterfall models. Because of this, finding software bugs before release is challenging.	7. In contrast to waterfall models, there are several opportunities to test the programme while it is being developed with a V model. Any issues in the software can be found and fixed more easily as a result before it is released.
8. Project goals, specifications, or plans cannot simply be modified in a waterfall model.	8. In the V model, modifications can be performed at any moment, in contrast to waterfall models, where it is difficult to modify the project's objectives and needs. V-models are a lot more versatile than waterfall models and other software development models because of this.
9. The risk management process is created specifically for each phase in waterfall models.	9. In V models, the risk management process is planned for every stage or phase, in contrast to waterfall models. It is superior to waterfall models because of this.
10. The entire project is completed before beginning a new phase in a waterfall model.	10. Work can be carried out on the phase or stage before beginning a new one in a V model, in contrast to a waterfall model. Compared to the waterfall model, it is significantly more adaptable.
11. Bug fixing is completed in waterfall models at the final stage of Phase 4.	11. In contrast to waterfall models, V models allow for issue correction at any point during all phases as well as stages. As a result, it is more adaptable than the waterfall model.
12. Debugging is completed at the final stage of Phase 4 in waterfall models.	12. In contrast to waterfall models, debugging can occur at any point during all phases and stages with V models.
13. Risk analysis is not appropriate in waterfall models.	13. Risk analysis is included in the V model.
14. In waterfall models, the work is completed in stages, and integration takes place at the end.	14. In V modules, the work is completed in phases rather than all at once.
15. One team works on a single phase in waterfall models.	15. In the V model, multiple teams work on various phases, as opposed to the waterfall model, which only has one team working on each phase.

Conclusion

The V model and the waterfall model are comparable in that they are both suitable for brief, predictable projects that aren't flexible or regularly changing. Numerous updated waterfall models that may solve some of the concerns about the original form have been produced in response to the limitations of the waterfall model. These include the models for rapid development, the "sashimi model" (a waterfall with overlapping stages developed by Peter DeGrace), the incremental waterfall model, the waterfall with subprojects, and the waterfall with risk reduction.

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