What is Iterative Model?

Software Development Life Cycle (SDLC) is extremely vast and full of various development and testing activities, methodologies, techniques, tools, and more. It involves intense planning and management, calculation and preparation. It is only after combining all these efforts of the software engineers that a software or application is successfully developed. Iterative Model is too a part of Software Development Life Cycle. It is a particular implementation of a software development life cycle that focuses on an initial, simplified implementation, which then progressively gains more complexity and a broader feature set until the final system is complete. In short, iterative development is a way of breaking down the software development of a large application into smaller pieces.

What is Iterative Model in Software Development Life Cycle (SDLC)?:

An iterative life cycle model does not start with a full specification of requirements. In this model, the development begins by specifying and implementing just part of the software, which is then reviewed in order to identify further requirements. Moreover, in iterative model, the iterative process starts with a simple implementation of a small set of the software requirements, which iteratively enhances the evolving versions until the complete system is implemented and ready to be deployed. Each release of Iterative Model is developed in a specific and fixed time period, which is called iteration.

Furthermore, this iteration focuses on a certain set of requirements. Each cycle ends with a usable system i.e., a particular iteration results in an executable release. Iterative Model allows accessing previous phases, in which the changes are made accordingly. The final output of the product is revived at the end of the Software Development Life Cycle (SDLC). Typically iterative development is used in conjunction with incremental development, in which a longer software development cycle is split into smaller segments that are built upon each other. Hence, iterative model is used in following scenarios:

  • When the requirements of the complete system are clearly defined and understood.
  • The major requirements are defined, while some functionalities and requested enhancements evolve with the process of the development process.
  • A new technology is being used and is being learnt by the development team, while they are working on the project.
  • If there are some high risk features and goals, which might change in the future.
  • When the resources with needed skill sets are not available and are planned to be used on contract basis for specific iterations.

Process of Iterative Model:

The process of Iterative Model is cyclic, unlike the more traditional models that focus on a rigorous step-by-step process of development. In this process, once the initial planning is complete, a handful of phases are repeated again and again, with the completion of each cycle incrementally improving and iterating on the software. Other phases of the iterative model are described below:

Iterative Model image

  1. Planning Phase: This is the first stage of the iterative model, where proper planning is done by the team, which helps them in mapping out the specifications documents, establish software or hardware requirements and generally prepare for the upcoming stages of the cycle.
  2. Analysis and Design Phase: Once the planning is complete for the cycle, an analysis is performed to point out the appropriate business logic, database models and to know any other requirements of this particular stage. Moreover, the design stage also occurs in this phase of iterative model, where the technical requirements are established that will be utilized in order to meet the need of analysis stage.
  3. Implementation Phase: This is the third and the most important phase of the iterative model. Here, the actual implementation and coding process is executed. All planning, specification, and design documents up to this point are coded and implemented into this initial iteration of the project.
  4. Testing Phase: After the current build iteration is coded and implemented, testing is initiated in the cycle to identify and locate any potential bugs or issues that may have been in the software.
  5. Evaluation Phase: The final phase of the Iterative life cycle is the evaluation phase, where the entire team along with the client, examine the status of the project and validate whether it is as per the suggested requirements.

Advantages of Iterative Model:

It is extremely necessary to know the advantages of the Iterative model, before implementing it in the Software Development Life Cycle (SDLC). The biggest advantage of this model is that, it is implemented during the earlier stages of software development process, which allows developers and testers to find functional or design related flaws as early as possible, which further allows them to take corrective measures in a limited budget. Other benefits or advantages of this model are:

  • Some working functionality can be developed and early in the software development life cycle (SDLC).
  • It is easily adaptable to the ever changing needs of the project as well as the client.
  • It is best suited for agile organisations.
  • It is more cost effective to change the scope or requirements in Iterative model.
  • Parallel development can be planned.
  • Testing and debugging during smaller iteration is easy.
  • Risks are identified and resolved during iteration; and each iteration is an easily managed.
  • In iterative model less time is spent on documenting and more time is given for designing.
  • One can get reliable user feedback, when presenting sketches and blueprints of the product to users for their feedback.

Disadvantages of Iterative Model:

Even though, iterative model is extremely beneficial, there are few drawbacks and disadvantages attached to it, such as, each phase of an iteration is rigid with no overlaps. Also, system architecture or design issues may arise because not all requirements are gathered in the beginning of the entire life cycle. Other disadvantages of iterative model are:

  • More resources may be required.
  • Although cost of change is lesser, but it is not very suitable for changing requirements.
  • More management attention is required.
  • It is not suitable for smaller projects.
  • Highly skilled resources are required for skill analysis.
  • Project progress is highly dependent upon the risk analysis phase.
  • Defining increments may require definition of the complete system.


A software is developed with several different techniques and methodologies. It requires tools, models, and other external elements to achieve successful completion. Iterative model, is one such development technique that allows small scale software development effortlessly. It is one of the key practises in Agile Development methodologies, in which steps are repeated as the project progresses with requirements. Iterative model iterates Requirements, Design, Build and test phases again and again for each requirement and builds up a system iteratively till it is completely built. Moreover, iterative model can accommodate changes in requirements, which are very common in most of the projects. It also provides an opportunity to identify and build any major requirement or design flaws throughout the process because of its iterative nature.