“Just starting of a software is not enough ,designing , implementing, testing, delivering and maintenance is

also necessary .”RamanDeep Singh

B.Tech,2nd YearGTBIT

Software Development Life Cycle (SDLC)

Contents For the Presentation➢Introduction➢Popular SDLC Models➢Waterfall Model➢ Iterative Model➢Spiral Model➢V-Model

IntroductionSoftware Life cycle is characterized by undertaking some particular steps being followed.These steps are often being defined differently according to the needs and the complexity of the project.These steps and how they would be executed collectively conceptualized the meaning of SDLC model.Different SDLC models defines different activities performed at each stage of the software development project in their particular way.

➢Waterfall Model.➢ Iterative Model.➢Spiral Model.➢V-Model.

Popular SDLC Models

Waterfall ModelThe waterfall model is a sequential methodology in which the progress of the software is seen as flowing steadily downwards through various phases.All the phases are cascaded to each other such that new phase cannot be started unless the previous one has been completed .Development moves from concept, through design, implementation, testing, installation, troubleshooting, and ends up at operation and maintenance. Each phase of development proceeds in strict order.

Pros and Cons of waterfall model➢ Pros:➢ The fixed phases of waterfall model implies discipline in the whole

software development process.➢ Tangible output at the end of each phase like SRS,SDD,etc gives path to

the future development.➢ The initial two phases gives the formal specification which helps in the

efficient knowledge transfer when team members are dispersed geographically.

➢ Cons:➢ The most notable con of the waterfall model is that customer do not know

the requirements at one go. ➢ Little opportunity for customer to preview the system . ➢ Designs that look feasible on paper turn out to be expensive or difficult in

practice, requiring a re-design and hence destroying the clear distinctions between phases of the traditional waterfall model. 

Iterative ModelThe idea behind the iterative model is to develop the system through repeated cycles and in smaller portions of time. In incremental model the whole requirement is divided into various builds. Each subsequent build of the module adds function to the previous release. The process continues till the complete system is ready as per the requirement. Development begins by specifying and implementing just part of the software, which can then be reviewed in order to identify further requirements. This process is then repeated, producing a new version of the software for each cycle of the model.

Pros and Cons of Iterative model➢ Pros:➢ Results are obtained early and periodically.➢ Parallel development can be planned.➢ Issues, challenges & risks identified from each increment can be

utilized/applied to the next increment.➢ Cons:➢ Defining increments may require definition of the complete system.➢ Not suitable for smaller projects➢ System architecture or design issues may arise because not all

requirements are gathered in the beginning of the entire life cycle.

Spiral ModeThe idea behind the iterative model is to develop the system through repeated cycles and in smaller portions of time. In incremental model the whole requirement is divided into various builds. Each subsequent build of the module adds function to the previous release. The process continues till the complete system is ready as per the requirement. Development begins by specifying and implementing just part of the software, which can then be reviewed in order to identify further requirements. This process is then repeated, producing a new version of the software for each cycle of the model.

Pros and Cons of spiral model➢ Pros:➢ Risk management is one of the in-built features of the model, which makes it

extra attractive compared to other models.➢ Issues, challenges & risks identified from each increment can be applied to the

next increment.➢ Project monitoring is very easy and effective. Each phase, as well as each

loop, requires a review from concerned people. This makes the model more transparent.

➢ Development can be divided into smaller parts and more risky parts can be developed earlier which helps better risk management. Cons:

➢ Not suitable for small or low risk projects and could be expensive for small projects.

➢ Large number of intermediate stages requires excessive documentation.➢ Skills required, to evaluate and review project from time to time, need

expertise.➢ Due to client feedback and subsequent customization and modifications

carried out in the various stages of development, reusing the prototypes in future projects becomes difficult.

V ModelThe V Model just like the waterfall model is sequential.All the processes take place in one after another in the developments cycle.The peculiar thing about V model is that testing of the product is planned in parallel with the process of the development cycle.In this model one phase start after previous one has started.It is also known for the strong verification and the validation processes involved in it.High confidence of customer is required for choosing the V-Shaped model approach. Since, no prototypes are produced, there is a very high risk involved in meeting customer expectations

Pros and Cons of V model➢ Pros:➢ Risk management is one of the in-built features of the model, which makes it

extra attractive compared to other models.➢ Issues, challenges & risks identified from each increment can be applied to the

next increment.➢ Project monitoring is very easy and effective. Each phase, as well as each

loop, requires a review from concerned people. This makes the model more transparent.

➢ Development can be divided into smaller parts and more risky parts can be developed earlier which helps better risk management. Cons:

➢ Not suitable for small or low risk projects and could be expensive for small projects.

➢ Large number of intermediate stages requires excessive documentation.➢ Skills required, to evaluate and review project from time to time, need

expertise.➢ Due to client feedback and subsequent customization and modifications

carried out in the various stages of development, reusing the prototypes in future projects becomes difficult.

More to come...Agile Model is now being widely used in the industry because of its substantial advantages.(Discussed in next slides to come).