The classic waterfall model is simple and attractive. However, because it cannot be used in actual software development projects, it is not a practical model. As a result, this model can be thought of as a theoretical approach to software development. The life cycle is divided into the following segments according to the traditional waterfall paradigm. 

• Study of Feasibility 
• Requirements Specification and Analysis 
• Integration and System Testing 
• Maintenance 
• Design 
• Integration and System Testing Maintenance 

Let’s take a look at each of these phases in more detail: 

1. Feasibility Study 

The primary purpose of this phase is to establish whether developing the programme is both financially and technically feasible. 

The feasibility study entails first establishing the problem and then determining the many feasible solutions. These many options are evaluated based on their benefits and downsides. The best solution is selected, and the next phases are carried out in accordance with this solution approach.

2. Requirements analysis and specification

The goal of the requirement analysis and specification phase is to fully comprehend the customer’s unique requirements and appropriately document them. There are two different activities in this phase. 

• Gathering and analysing requirements: All software requirements are first acquired from the customer, and then the gathered needs are assessed. The analysis section’s purpose is to eliminate inconsistencies and incompleteness (an incomplete requirement is one in which certain aspects of the real requirements have been deleted) (an inconsistent requirement is one in which some part of the requirement contradicts some other part).
• Software requirement specification (SRS) document: These analysed requirements are described in a document called a software requirement specification (SRS). Customers and the development team sign the SRS document as a contract. The SRS document can be used to resolve any future disputes between customers and developers.

3. Design 

The purpose of this step is to translate the SRS requirements into a format that can be written in a computer language. It encompasses both high-level and detailed design, as well as overall software architecture. All of this work is documented in a Software Design Document (SDD).

4. Coding and unit testing

During the coding phase, the software design is converted into source code using any programming language that is appropriate. As a result, every designed module is coded. The goal of the unit testing step is to see if each module is functioning properly.

5. Integration and system testing

After each module has been coded and unit tested, it is time to put it all together. The integration of several modules is done in stages over a period of time. Previously designed modules are added to the partially integrated system throughout each integration stage, and the resultant system is tested. Finally, after all of the modules have been successfully integrated and tested, a complete functional system is obtained, and system testing is performed. 

There are three types of testing activities in system testing, as stated below:

• Alpha testing: It is a type of system testing carried out by the development team. 
• Beta testing: It is the process of putting a system through its paces with a small group of willing testers. 
• Acceptance testing: After the software was delivered, the customer conducted acceptance testing to evaluate whether the software should be accepted or rejected.

6. Maintenance

The most critical phase of the software life cycle is maintenance. Maintenance takes up 60% of the time it takes to design a whole piece of software. Maintenance can be divided into three categories: 

• Corrective Maintenance: It is performed to remedy problems that were not found during the product development process. 
• Perfective Maintenance: This type of maintenance is performed to improve the system’s functionality in response to a customer’s request. 
• Adaptive Maintenance: When porting software to a new environment, such as working on a new computer platform or with a new operating system, adaptive maintenance is frequently required.

The Benefits of the Traditional Waterfall Model 

The waterfall model is a romanticised version of software development. Because it is so basic, it can serve as a foundation for different software development life cycle models. Some of the primary benefits of this SDLC methodology are listed below: 

• This model is straightforward and easy to comprehend. 
• In this model, phases are handled one by one. 
• The model’s stages are all properly described. 
• The milestones in this approach are highly obvious and well-understood. 
• The process, activities, and outcomes are all meticulously documented. 
• Good habits are reinforced: define before designing and designing before coding. 
• This paradigm works effectively for smaller projects and those with well-defined requirements.

The Classical Waterfall Model has a number of flaws 

We can’t utilise the classic waterfall model in real projects because of its flaws; instead, we use other software development lifecycle models that are based on the original waterfall model. The following are some of the model’s key flaws: 

• No feedback path: In the traditional waterfall paradigm, software evolves from one phase to the next in a cascade-like fashion. It is assumed that no errors are made by developers at any time during the development process. As a result, it lacks any sort of error-correcting mechanism.

• Vary requests are difficult to accommodate: This approach implies that all client requirements can be thoroughly and correctly defined at the start of the project, but in reality, customers’ requirements change over time. After the requirements specification step is completed, it is difficult to accommodate any change requests. 

• No phase overlap: According to this approach, a new phase should only begin after the preceding one has been completed. This, however, cannot be maintained in real-world enterprises. Phases may overlap to improve efficiency and cut costs.