Waterfall Model

 

 Waterfall Model 

• It is also referred to as a linear-sequential life cycle model. 
• WATERFALL MODEL is a sequential model that divides software development into pre-defined phases. 
• Each phase must be completed before the next phase can begin with no overlap between the phases.
• Each phase is designed for performing specific activity during the SDLC phase. 

Sequential Phases

• Requirements: The first phase involves understanding what needs to design and what is its function, purpose, etc. Here, the specifications of the input and output or the final product are studied and marked.
• System Design: The requirement specifications from the first phase are studied in this phase and system design is prepared. System Design helps in specifying hardware and system requirements and also helps in defining overall system architecture. The software code to be written in the next stage is created now.
• Implementation: With inputs from system design, the system is first developed in small programs called units, which are integrated into the next phase. Each unit is developed and tested for its functionality which is referred to as Unit Testing.
• Integration and Testing: All the units developed in the implementation phase are integrated into a system after testing of each unit. The software designed, needs to go through constant software testing to find out if there are any flaws or errors. Testing is done so that the client does not face any problem during the installation of the software.
• Deployment of System: Once the functional and non-functional testing is done, the product is deployed in the customer environment or released into the market.
• Maintenance: This step occurs after installation, and involves making modifications to the system or an individual component to alter attributes or improve performance. These modifications arise either due to change requests initiated by the customer, or defects uncovered during live use of the system. The client is provided with regular maintenance and support for the developed software.

 
Waterfall model can be used when,

• Requirements are not changing frequently
• Application is not complicated and big
• Project is short
• Requirement is clear
• Environment is stable
• Technology and tools used are not dynamic and is stable
• Resources are available and trained

 

Advantages In this model, phases are processed and completed one at a time and they do not overlap. Before the next phase of development, each phase must be completed. Suited for smaller projects where requirements are well defined. They should perform quality assurance test (Verification and Validation) before completing each stage. Any changes in software is made during the process of the development.

Disadvantages It is difficult to estimate time and cost for each phase of the development process.  Error can be fixed only during the phase. It is not desirable for complex project where requirement changes frequently. Testing period comes quite late in the developmental process.. Small changes or errors that arise in the completed software may cause a lot of problems.