Software Development Life Cycle (SDLC): Definition, Models, And Phases

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In the fantastic world of development there is a certain framework that developers use to produce high-quality software efficiently and cost-effectively. This framework eables businesses to follow the development process in a clear and methodical way.

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It’s called software development life cycle. And as all frameworks, it has its standard steps and procedures. In this article we’ll go through the definition of software development cycle. We’ll address its models, then switch to different SDLC phases and go through those in a bit more detail.

Let’s dig in!

What is Software Development Cycle?

The software development life cycle or SDLC is an essential tool used in software development. It evolved over the years and improved the way programs are created. It makes it easier for engineers and programmers to comprehensively build programs of all sizes.

The SDLC consists of individual steps that are required to plan, develop, and implement software programming. Each step is vital in the successful creation and roll-out of a system. Every process can have several layers that all play essential roles in the process.

The software development life cycle is cyclical in nature as the process is ongoing. It’s also common to have to react and move forward and backward through the steps for various reasons. Not to mention that processes can often overlap or occur simultaneously.

5 Important Software Development Life Cycle Models

There are several models of the cycles and each one lends itself to different applications. They all consist of the same basic steps that are equally important. Moreover, each can be adjusted to work better for specific teams or projects.


Picture 1. Software development life cycle model

1. The Waterfall Model

A model where steps are performed in order. Each process depends on the completion of the previous one. It is the simplest process and requires careful step-by-step data tracking. It is also easy to manage the steps but note that the rigidness can lead to more risk.

2. The V-Model

A more complex version of the waterfall model. It expands on the process by adding testing related to every step in the process. This can lead to the discovery of issues early in the process. But like the waterfall model, it can lead to risks from the lack of flexibility.

3. The Iterative Model

It moves on a cyclical continuum of completing incremental pieces of a larger project. The individual pieces can be completed simultaneously in small chunks. This allows for flexibility if the project needs to grow along the process. However, the iterative model can make large projects tough to manage and can drain resources.

4. The Spiral Model

Combines the waterfall and iterative models. It puts a strong focus on analyzing risk at every stage in the process. This model breaks the project into smaller releases that cycle through each phase of the complete process. It can require a significant investment but can help identify issues very early on.

5. The Agile Method

Concentrates on the experience and satisfaction of the customer or end-user of the program. Developers receive feedback throughout the process and adjust as needed. This flexible model results in knowing that the end-user is satisfied. But it can make it difficult to initially plan for the time and resources needed to complete the project.

Important to realize that each model uses a varying combination of the same general steps and techniques. The stages may be completed in different orders or multiple times according to the model. However, they all include the same basic definitions.

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7 Software Development Life Cycle Phases

1. Planning

The planning step is the first stage of any project. It requires a careful analysis of the financial and human resources required to complete the task. The timeline is also established during this phase.

Above all, the planning phase includes determining if the project is feasible with existing resources. All stakeholders must work together. Why? To decide if the project can be completed within the desired budget with the current team. Moreover, making adjustments and creating the expectations of the project should be completed at this phase.


Picture 2. Planning phase

2. Requirements

The requirement stage involves working with the customer or end-user to determine the requirements of the system. The desired uses should be precisely defined at this stage. With this in mind, t’s important to make sure the system will meet all of the needs of its intended purpose.

Going through scenarios and how the system can be used is helpful in design. The system requirements can be communicated clearly to all stakeholders. It is essential that these requirements are clear and approved before work begins.

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3. Design

The design process can begin once a clear list of requirements is established. Designers can map how the components will work together. It will include the framework that the coding can be based on.

The general design has to be reviewed to make sure the software can be supported and operated within the organization’s constraints. The end-user will also make sure all desired features and needs that must be met are included. So, this process is certainly essential to the foundation of the development of the software.

4. Development

This phase is where the software is actually developed. The code is specifically written to address the predefined requirements. The steps within this phase can vary depending on the SDLC model that can be used. 

Unit testing and adjustments are included in this phase. CICD programs are helpful during this period to automate the ongoing testing of the code being written. The result of this phase should be a complete, working program.


Picture 3. Development phase

5. Testing

The testing phase is essential in ensuring a system works properly. It is the most important phase in developing quality, functional software. It’s also helpful to complete the testing phase in several layers to be thorough.

The testing process should repeat, layer by layer, with corrections made along the way. Testing interactions with other systems and making sure the system can handle the expected number of users is vital. Altogether, the testing process should continue until all of the discovered flaws are eliminated and the system is ready for deployment.

Read A/B Testing.

6. Deployment

With the deployment process, timing is everything. A delay is usually better than a problematic deployment. It’s vital to make sure the software is free of problems for a successful program release. Furthermore, it’s also wise to plan deployment for times when it’s less likely that issues could affect productivity like nights or weekends.

The software system is then deployed to begin it’s planned usage. It may be better to launch separate pieces of the program in phases if it’s a large system. After all, this makes addressing unforeseen problems much more manageable.

7. Operations and Maintenance

The last phase is support operations and it’s an ongoing process. Above all, this phase focuses on ensuring that the system is performing correctly. It includes continuous maintenance and troubleshooting any issues.

In the operations and maintenance phase, a help desk is typically formed to support program users. The entire software development life cycle may be applied to correcting any bugs detected in the system. Routine software updates and patching operations are part of this phase.

Read Helpdesk Guide for Beginners.


In conclusion, different models of the software development life cycle are applicable to different projects and applications. The intended use and requirements of the software can help to decide which model to use. The available time and resources can also be a deciding factor.

It’s important to note that each distinct process in the life cycle plays a vital role in developing a quality software product. They are reliant on each other and the efforts combine to create a highly-functional, error-free result.

Given these points, the SDLC is a great tool to help coordinate and communicate across functions for a seamless development process.

Gabe Nelson is a content specialist of over 7 years of experience,  currently working for Just out of high school he set off crab fishing on the Bering sea in Alaska. From there he went back home to finish his college degree at the University of Montana. He is a vivid reader who likes to read about hacks and tricks to be applied for businesses to grow faster.

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Software Development Life Cycle (SDLC): Definition, Models, And Phases was last modified: June 23rd, 2021 by Milica Vujasin
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