SDLC- Iterative model

Generally, in all other model we begin the process with a complete requirements specification. But in the Iterative model does not attempt to begin with a complete specification of requirements and the iterative process begins with a very small part of implementation of the requirements and enhances the versions iteratively until the implementation of the system completes and ready to be deployed and each iteration produces a new version of the product at the iteration end of the model.

When to use iterative model:

• Whenever there is larger project i.e. with number of modules.
• Only some important requirements are defined and some other details can evolve with time.
• When the system has clear and completely defined requirement

 Advantages:

• In the early stage of the life cycle, we can develop and make few functionalities works quickly.
• Requirements changes are allowed
• It supports changing requirements
• Application is produced at early stage where customer can evaluate and give the feedback.
• Suitable for complex and larger projects. Example: mission-critical / life critical projects.
• Changes / Modifications in the requirement is not much costlier
• In this model we can measure the progress
• Since this has iteration process, testing and debugging is easier
• We can plan for parallel development

 Disadvantages: 

• It is not suitable for smaller projects
• Progress of Project is mainly depending upon the risk analysis.
• For risk analysis, experience skilled resources are required.
• Requires more number of resources.
• An iteration of each phase is rigid