Understanding Software Development Life Cycle (SDLC) | SDLC Phases And Models

Software Development Life Cycle - Working Phases and Models

Software Development involves several steps. The developers follow a systematic framework called Software Development Life Cycle (SDLC) to design, develop, test, and maintain high-quality software that meets the customer’s expectations. Today, we will discuss SDLC working, different phases, and models of SDLC.

What is Software development Life Cycle SDLC?

Software Development Life Cycle (SDLC) is a process that consists of a flow of steps to develop, test, alter, and enhance a software product. The Life Cycle defines detailed methods to deliver high-quality Software. In simple words, SDLC plans the complete cycle that the software product transits through from its initiation to retirement. It has several stages in which the software is processed and any SDLC phase may perform more than one activity.

Need of SDLC

The main objective of SDLC is to deliver high-quality software that meets and exceeds customer expectations.
To develop an efficient software product, the development team must have a detailed Life cycle model that the software goes through.

  • Proceeding without a suitable Life Cycle model for software development, the product development will most probably deviate from the right track.
  • The process of Development will be disciplined and systematic only when the team follows a suitable Life Cycle model for Software Development.
  • The team must have an understanding of what to do and what not to, how work is distributed, etc, or else it may lead to the project failure.
  • Without the Software Life Cycle (SDLC), it becomes difficult for software developers and managers to monitor the progress of their projects.

How SDLC works?

Software Development Cycle (SDLC) is the representation of the Software Development process. It works by lowering the cost of operation while increasing the product quality and decreasing production time. SDLC eliminates these divergent pitfalls of software development programs by following a systematic plan that starts with the evaluation of systems for deficiencies.

Then it defines the new system requirements. Next, it builds the software through the phases of Analysis, planning, design, development, testing, and deployment. Now, let’s explore SDLC phases and steps.

software development life cycle(sdlc)

Source: javaTpoint

7 Phases of Software Development Life Cycle 

Following are the stages of the Software Development Cycle

1. Planning And Requirement Analysis

Before creating the product, it is important to acquire the core knowledge and understanding of the product. Requirement analysis is a crucial and necessary phase in SDLC. The Business analyst and Project Organizer gather the data such as customer requirements, who is the end-user, and the objective of the product.

In the same phase Identification of risk associated with the project and planning for the quality assurance is also done.

2. Defining The Requirements

In this phase, representation and documentation of the software requirements take place. This is done through the Software Requirement Specification (SRS) document.

The SRS document contains all the software product requirements that are to be constructed and developed during the Systems Development Life Cycle. Any ambiguities must be resolved in this phase only.

3. Designing The Software

Next, the gathered requirements in the SDLC phases are documented and turned into a design plan termed as Design Document Specification (DDS). Then all the stakeholders are allowed to review and ask for feedback about DDS and the best design approach is selected from the Proposed architectures. DDS consists of all the minutest details of the internal design of all the modules of the proposed architecture.

4. Developing The Project (Coding)

The actual development of the product starts in this phase of the SDLC, also the Programming is built. Implementation of design starts with the writing of code. In this step, the Software design is translated into the source code and all the components of the software are implemented. Developers follow the coding guidelines by the programming tools and management to develop and implement the code.

5. Testing The Software

After the code is ready, it is sent to the testing team. It is tested against the requirements and any defects found are assigned to the developers to get them fixed. Once the code is ensured to be error-free, it goes to the implementation phase and the outcome will be a high-quality product. In this phase, unit testing, integration testing, system testing, acceptance testing are performed.

6. Deployment In The Market

Once the code is ready, it is deployed into the appropriate market. Sometimes it may happen phase-wise based on the business strategy or User Acceptance Testing (UAT) is done where developers along with the customers do the testing. UAT is the replica of the production environment.

7. Maintenance

Maintenance starts once the software is deployed. Once the real users come up, any issue arises and needs to be fixed or any enhancement required is to be taken care of by the development team. This process of taking time-to-time care of the developed product is known as Maintenance.

Software Development Life Cycle ( SDLC) Models

The software life cycle model is a depictive representation of the SDLC. Following are the Software Life Cycle Process models.

1. Waterfall Model

It is the basic model that is used in SDLC and is also known as the linear sequential model. In this model, the output of the first phase acts as the input for the next phase. Only after the completion of the first phase, the development of the next phase starts.

sofware life cycle

Source: javaTpoint


  • It is the most simple model, easy-to-understand, and a step-by-step process.
  • It makes the project easily manageable as the deliverables of each phase are well defined.


  • It cannot be used in short-duration projects as the new phase does not start until the completion of the first phase.
  • The waterfall model cannot be used in projects whose requirements are continuously changing because any change will lead to alteration in every phase.

2. V-shaped Model

It is also known as the verification and validation model. Here the development and testing go hand in hand. Unlike the waterfall model, test planning and testing start at an early stage in the V-shaped model.
The verification phase involves requirement analysis, system design, high-level design, low-level design, and coding.

sdlc models

Source: ResearchGate


  • V-shaped model is a systematic and disciplined model and the outcome is a high-quality product.
  • It is a simple and easily understandable SDLC model.


  • In the V-shaped model, Requirement change at any later stage would cost too high.
  • This model is not suitable for the ongoing projects

3. Prototype Model

In this model, the prototype is developed preceding the actual software. It has limited functional capabilities and comparably inefficient performance. Feedbacks from the customer are implemented and the prototype is again reviewed by the customer for any change. This process is repeated until the customer is satisfied with the model. After the customer accepts the model, the final product is built.

Software Development Process

Source: Tutorial & Example


  • It detects the defects much earlier and thereby reduces the cost and time of the allotment.
  • Any requirement change can be identified in the evaluation phase and implemented in the refined prototype.


  • The involvement of the customer in every phase can change the end product requirement and thereby increases the complexity, delivery time of the product

4. Spiral model

The phases of this model follow the iterative method. Loops in this model represent the various stages of SDLC. The innermost loop i.e requirement gathering and analysis follows spiral model phases and the next loop is designing, implementation and testing.
The spiral model has four phases they are

  • Planning
  • Risk analysis
  • Engineering and
  • Evaluation

Software development life cycle phases

Source: Search Software Quality


  • Any changes in the later status can be done in the next iteration.
  • Here risk analysis is done extensively using prototype models, this makes the spiral model less complex


  • It is mostly recommended for large projects only.
  • As it can reach a high number of iterations the cost can also be high.

5. Big Bang Model

This model does not have any well-defined procedure. It does not require any planning or scheduling. The outcome of the model is a developed product that might be or might not be the need of the customer. The developer does only the requirement analysis and coding.

Software life cycle process model

Source: ProfesionalQA


  • Bigbang is a simple model where much planning and scheduling are not required.
  • The developer can develop the product as per his flexibility and understanding.


  • It cannot be used for large, complex, or ongoing projects.
  • There is no dedicated testing team and formal testing is not done.

6. Iterative Incremental Model

It divides the project into small parts known as iterations. Each small chunk of the project goes through the phases. After the completion of the iteration, a verified product is delivered to the customer for evaluation and feedback. Feedback from the customer is implemented in the next iteration. Therefore, the product increments in terms of features, and the final build product hold all the features added in intermediate iterations.

Following are the phases of the iterative and incremental development model

  • Inception phase
  • Elaboration phase
  • Construction phase and
  • Transition phase


sdlc models in software engineering

Source: Wikimedia Commons


  • In this model, the risk is properly analyzed and identified in iterations.
  • The division of the project into small chunks makes the product easy to manage.


  • To incrementally break down and build, you need to have a complete requirement and understanding of the product.

7. Agile Model

The Agile Model primarily focuses on the flexibility of developing a product. This is a combination of iterative and incremental models. The product is broken into small incremental builds and is developed separately. Each build increments in terms of features. In this model, iterations are known as sprints and each sprint lives for 2 to 4 weeks. The products verified by the owner are delivered to the customer at the end of each sprint. The feedback from the customers is included in the next sprints same as in the iterative method.

software development life cycle models

Source: javaTpoint


  • Agile model offers more flexibility to adapt to the changes and current new features can easily be added.
  • Every phase collects customer feedback for enhancement.


  • This model needs highly skilled resources and it lacks documentation.
  • This model is not recommended when the customer is not clear about his product requirements.


Following a suitable development life cycle is crucial for the successful completion of a project. Every SDLC model has its pros and cons. They are not ranked, developers should choose the model according to their requirements.

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