Everything about SDLC and its Models

Mamta Mitali

Jul 16, 2021
Everything about SDLC and its Models

Application security is a critical part of developing modern software. As the internet becomes more complicated, attackers are increasingly relying on known security weaknesses and vulnerabilities in software. To avoid data breaches, businesses must incorporate security into all phases of software development, testing, and deployment. 

Examining the software development lifecycle, or SDLC, is one method to prepare for this. SDLC, is an acronym for Software Development Life Cycle

This article will offer you an overview of the SDLC basics, available SDLC models, and their usage in the industry.

What is SDLC?

SDLC is a planned method for developing software that ensures its quality and correctness. Through SRS (Software requirement specification), the SDLC process seeks to develop high-quality software that satisfies client needs. The system development should be completed within the schedule and budget constraints. SDLC is a step-by-step process that outlines how to plan, develop, and maintain software. Each phase of the SDLC life cycle includes its own set of processes and deliverables, which feed into the next. The SDLC is also known as the Application Development Life Cycle (ADLC).


The following are some of the most essential reasons why SDLC is crucial while designing a software system:

  1. It serves as a foundation for project planning, scheduling, and costing.

  2. Provides a framework for a group of activities and deliverables.

  3. It's a system for keeping track of and controlling projects.

  4. Increases the visibility of project planning to all development process stakeholders.

  5. Speed of development has been increased and improved.

  6. Client relationships have improved.

  7. Assists you in lowering project risk and reducing project management plan overhead.

What are the different SDLC Phases?

The complete SDLC process is broken down into seven stages:

Phase 1: Requirement gathering and analysis

Phase 2: Feasibility study

Phase 3: Design

Phase 4: Coding

Phase 5: Testing

Phase 6: Deployment

Phase 7: Maintenance

Let's go over each phase one by one:

Phase 1: Requirement gathering and analysis: It is organized by senior team members with input from all industry stakeholders and domain specialists. At this point, the quality assurance requirements are planned for, as well as the risks associated. This stage provides a clearer understanding of the project's overall scope as well as the expected difficulties, opportunities, and instructions that prompted it. Teams must gather specific requirements and exact criteria throughout the gathering step. This aids companies in determining the necessary timeline for the software's completion.

Phase 2: Feasibility study:  Core team identify and document software requirements. The 'Software Requirement Specification' document, also known as the 'SRS' document, was used to carry out this process. It covers everything that needs to be planned and developed during the Application life cycle.

Phase 3: Design: The requirement specification document is used to create the system and software design documents. This aids in the design of the overall system architecture.

During this phase, two types of design documents are created:

High-Level Design (HLD)   

  1. Each module's name and a brief explanation

  2. An overview of each module's functionality.

  3. Module dependencies and interface relationships

  4. The key elements of database tables have been determined.

  5. Diagrams of the entire architecture, as well as technology specifics

Low-Level Design (LLD)

  1. The modules' functional logic

  2. Tables in the database that provide information such as type and size

  3. All forms of dependency difficulties are addressed.

  4. Error messages are listed below.

  5. Every module's complete input and output.

  6. Complete detail of the interface.

Phase 4: Coding: After the system design phase, the coding step begins. Developers begin building the entire system in this phase by developing code in the programming language of choice. Tasks are separated into sections or modules and given to different developers during the coding phase. It is the most time-consuming step of the Software Development Life Cycle. Developers must adhere to a set of predetermined code principles. They must also produce and implement code using programming tools such as compilers, interpreters, and debuggers.

Phase 5: Testing: When the software is finished, it is put into the testing environment. The testing team begins testing the full system's functionality. This is done to ensure that the entire application functions as expected by the customer. The QA and testing teams may discover problems or defects, which they report to the developers. The development team fixes the issue and sends it back to QA for another round of testing. This procedure is repeated until the programme is bug-free, stable, and meets the system's business requirements.

Phase 6: Deployment: The final deployment procedure begins after the software testing step is completed and there are no defects or errors remaining in the system. The final software is released and tested for deployment faults, if any, based on the project manager's feedback.

Phase 7: Maintenance: Following are the three activities that occur once the system is deployed and clients begin to use the developed system.

Bug fixing - Issues are reported as a result of some circumstances that have not been thoroughly tested.

Upgrade - Upgrading the software application to a newer version.

Enhancement -Adding new functionality to an existing piece of software.

SDLC Models

During the software development process, numerous software development life cycle models have been established and designed. Software Development Process Models are another name for these models. To assure success in the software development process, each process model follows a set of stages specific to its type.

The most essential and widely used SDLC models in the industry are listed below:

  1. Iterative Model

  2. Spiral Model 

  3. V-Model 

  4. Big Bang Model 

  5. Waterfall Model

Agile Model, RAD Model, Rapid Application Development, and Prototyping Models are all similar methods.

Let’s take some famous models:

Waterfall Model: In the software development process, the waterfall model follows a sequential order. It indicates that the project team will only move on to the next step of the SDLC if the previous phase has been satisfactorily completed.

  1. First, requirements are gathered and analysed. Only after the requirement has been frozen can the System Design begin. The SRS document developed in this case is the result of the Requirement phase and serves as an input to the System Design phase.

  2. Documents that serve as input for the next phase, i.e. implementation and coding, are prepared in System Design Software Architecture and Design.

  3. Coding is completed in the Implementation phase, and the software created serves as the basis for the next phase, testing.

  4. The created code is rigorously checked throughout the testing process to uncover software faults. Defects are recorded in a defect tracking tool and retested once they've been rectified. Bug logging, retesting, and regression testing continue until the software is ready to go live.

  5. After the customer has given his or her approval, the developed code is moved into production in the Deployment phase.

  6. Any issues that arise in the production environment are dealt with by the developers who are in charge of maintenance.

Here is a graphical illustration of the Waterfall Model: 

Advantages of the Waterfall Model:

  1. This model is straightforward to implement, and the resources required are small.

  2. The requirements are simple and transparent, and they remain constant throughout the project's development.

Disadvantages of Waterfall model:

  1. Because the risk factor in this model is higher, it is not appropriate for more significant and complex projects.

  2. This model seems unable to adjust to changes in needs as they occur during development.

Agile Model: The Agile Model combines the Iterative and Incremental approaches. Rather of focusing on the requirement, this model providing when designing a product. A product is broken down into small incremental builds in Agile. It is not created as a whole product all at once. In terms of features, each build improves. The following version is based on the previous version's features.

In agile iterations are termed as sprints. Each sprint lasts between two and four weeks. The product owner verifies the product at the end of each sprint, and following his approval, it is sent to the customer. Customer input is gathered in order to improve the product, and his ideas and enhancements are implemented in the following sprint. Each sprint includes testing to reduce the risk of failure.

The advantages of the Agile Model:

  1. Is a highly realistic software development technique.

  2. Promotes interaction and cross-training.

  3. Functionality can be demonstrated and built quickly.

  4. The number of resources required is little.

  5. Adaptable to a variety of requirements, both fixed and variable

The disadvantages of the Agile Model:

  1. Not recommended for dealing with complex dependencies.

  2. There is a greater danger of long-term viability, maintainability, and extensibility.

  3. It will not work without an overall plan, an agile leader, and an agile PM practise.


The software development models that are chosen for projects are frequently influenced by a number of factors. These factors include the required level of skill, business requirements, and the amount of time and money available for the SDLC process. To make an informed judgement, a software engineer must be well-versed in all SDLC approaches. They can then choose the one that is most appropriate for the project at hand. 

We hope you got a better understanding of “STLC and its models” by reading this article!

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