Waterfall model and spiral model are used in software development life cycle or SDLC. Any software development process follows one of these models depending on the type of software and the requirements of the customer.
Waterfall model
This model is called as sequential model since it works in stages. The output of first stage becomes the input of the second stage.
The errors of the first stage can be rectified only when it is completed. This is time consuming and makes the process lengthy. Stage 1 is completed before stage 2 begins.
The six stages involved in waterfall model are Requirement Gathering and analysis, System Design, Implementation, Integration and Testing, Deployment of system, and Maintenance.
Spiral model
This model is implemented in iterations. It is also called evolutionary model.
Initially a prototype of the system is prepared. Then, it is followed by development of small parts of the system.
These smaller parts are then assembled to produce the final system.
The four stages which form the spiral model are Identification, Design, Development and Evaluation and Risk Analysis.
The differences between the two models are summarized below.
1. Waterfall model works in linear method. Spiral model follows evolutionary method.
2. Errors and risks are discovered/ rectified after the stage is over. Errors and risks are discovered/ rectified earlier.
3. Waterfall model is suitable for small projects. Spiral model is suitable for large projects.
4. Requirements identification and planning is the initial stage in the waterfall model. Requirements identification and planning is done when needed, in the spiral model.
5. Waterfall model allows little to no flexibility in the system. Spiral model allows flexibility in the system.
6. Low flexibility makes the waterfall model more risky. High flexibility makes the spiral model less risky.
7. Waterfall model, overall, takes less time since requirements are clear. Spiral model is implemented when the requirements of the system are not clear and become clear through prototypes.
