Software Development Life Cycle vs Agile: Key Differences Explained

The approach you take to building software can have a big impact on the final outcome. Over the years, people have come up with different approaches to make the process smoother and more reliable. The two approaches that are used a lot are SDLC and Agile.

SDLC is all about following a structured, step by step process to develop software, while Agile is more about being flexible and making quick changes as you go. 

But how do you figure out which approach is the right one for your project? Let’s break it down and explore their key differences.

What is the Software Development Life Cycle (SDLC)? 

The Software Development Life Cycle is a structured process that helps develop high-quality software It guides developers through different phases, starting from planning design to coding, testing, and finally delivering the software.

Guide for Software Development Life Cycle

Each phase has a particular purpose. For example, the planning phase focuses on identifying what the project aims to achieve and what it needs. During the design phase, developers outline a plan for how the software product will work. 

Then comes the coding, where the actual software is built, followed by testing to make sure it works perfectly before it’s released.

SDLC guarantees that software is developed in a structured and organized way. It lets software development teams save time, manage resources, and deliver reliable solutions. It’s not just for software, it can also be used for developing hardware components too.

Learn how to create Project Management Plan for Your Software Development

Teams can reduce mistakes, meet user expectations, and create working software by following SDLC.

Phases of SDLC

SDLC is broken down into several phases, each has an important role in building successful software.

1. Planning

The planning phase is where everything starts. The software development team collaborates with the customer to understand what the software needs to do. This includes discussing the purpose of the application, who will use it, how it should look, and the basic features it should have, including the overall user interface design.

These requirements are then recorded in a Software Requirements Specification (SRS) document. 

2. Requirement Analysis

In this phase, the project team carefully studies what the software needs to do. This includes understanding user needs, collecting feedback from stakeholders, and defining how the system should work. 

The team also looks at security needs, checks for risks, and notes any specific limitations of the software. All these details are added to the Software Requirements Specification (SRS) document.

3. Designing

In the design phase, the team prepares a plan that outlines how the software will function. This includes the overall system architecture, hardware requirements, and programming language framework.

The design is based on the SRS document to align the software with the client’s needs. All the details are recorded in the Design Document Specification (DDS) and reviewed by stakeholders for feedback. 

4. Implementation

The implementation phase, developers begin writing the code needed to build the software. They use tools like code editors, debuggers, and compilers to write and test the software.

The software is built module by module, and each part is tested separately to make sure it works properly.

5. Testing

In the testing phase, the software is evaluated to confirm it performs as intended. The quality assurance team tests the software to find any errors or bugs and sends them back to the developers for fixing.

Testing includes processes like integration testing, where two modules are tested together, and system testing, which checks the entire software. This step is repeated until the software is stable, error-free, and ready to use.

6. Deployment

At this stage, the software is made available to users. The development team sets up the installation process so customers can start using it.

Once the software is live, feedback from users can help improve the product or add new features. Existing customers also get maintenance and support services so the software continues to function properly.

7. Maintenance

The maintenance phase begins once the software is live and users start using it. If they face any bugs or issues, the development team fixes them to keep the software running smoothly.

This phase also includes regular updates and improvements to make the software better over time. It’s important to keep checking and tracking the software to make sure it delivers the expected value.

What is Agile Methodology?

Agile methodology is a popular way to develop software because it focuses on being flexible and responding to changes. With this approach, the project is divided into smaller sections and delivered in short cycles. This lets teams get fast feedback, make improvements, and then adjust as required.

Agile works through cross-functional teams made up of testers, product owners, and developers working closely together. It focuses on customer feedback and interactions within the team to build solutions.

There are several Agile frameworks like Lean, Scrum, Extreme Programming, and Kanban, which help teams plan and deliver projects step by step. 

Learn Key Agile Concepts

Agile is basically a mindset inspired by the Agile Manifesto from 2001, which introduced 4 values and 12 agile principles for better software development.

Software Development Life Cycle Models

There are any SDLC models, and each comes with its own strengths and limitations. No single model works perfectly for every project, so the choice depends on the needs of the software, the team, and the goals of the project.

Here are five of the most popular SDLC models that teams often use today.

1. Agile Model

The Agile model is built to handle changing requests accurately and quickly. It divides the project into smaller sections and completes them in quick cycles. This way, teams can get feedback early and make changes along the way.

The primary aim of the this model is to finish the project faster while meeting customer satisfaction. It brings the agile team and customers together to work closely.

2. Iterative Model

The Iterative model develops the software in small steps. After each cycle, a working version of the software is created, but it’s not fully complete. With every new cycle, more requirements are added to improve the software bit by bit.

The final cycle delivers the complete software with all the required features. 

3. Waterfall Model

The Waterfall model is among the earliest and most straightforward SDLC approaches. It uses a structured process where every phase needs to be completed before starting the next.

Once a phase is complete, changes cannot be made, which makes the model less adaptable. This is why the Waterfall model is rarely used today. However, it is still important because it forms the basis for many other SDLC models. 

4. Spiral Model

The Spiral model is designed to handle risks during software development. It works in loops, where each loop represents a phase of the project. 

This model combines planning, risk analysis, development, and testing in each loop. By repeating these steps, the software improves gradually while handling risks.

5. V-Shaped Model

The V-shaped model follows a systematic process in the shape of a “V.” Each development phase is directly connected to a testing phase. After the development stage is complete, testing is performed  to check everything functions as intended.

This model is also known as the Verification and Validation model.

Difference between SDLC and Agile

SDLC and Agile are widely used methods for software development. Below are the key differences between them:

Agile	SDLC
Agile is a step by step method where projects are delivered in small, working chunks.	SDLC follows a fixed process, where each phase like planning, design, and testing is completed one after the other.
It helps teams to adapt to changing requirements quickly during development.	It does not allow changes once the phases are locked in, unlike agile development.
Agile focuses on regular input from team members and customers to enhance the product.	The complete product is provided only after finishing the full development process.
It encourages continuous improvement through regular reviews and updates after each iteration.	SDLC depends heavily on detailed documentation at each stage to guide project managers and developers.
Agile works best for agile projects where flexibility is important.	Collaboration is structured, with customers involved mainly at the start and end.
The software is tested at every stage after small parts are completed, with sprint planning ensuring steady progress.	It works well for large, well-defined projects where requirements do not change.
Agile teams work to deliver a Minimum Viable Product (MVP) early to get feedback.	Testing happens only after the full product is developed, and it does not focus on continuous improvement during development.

Follow these Guidelines for Agile Development

Pros of SDLC and Agile

Both SDLC and Agile offer different advantages. Let’s explore what makes them valuable for different types of projects.

Pros of SDLC

• Makes project development clear and organized with a well-structured process
• Reduces risks by spotting and managing challenges early in the project
• Gives detailed documentation that’s helpful for future maintenance and reference
• Keeps project progress predictable with clear phases and timelines
• Clearly outlines roles and tasks so everyone understands their responsibilities
• Works best for large projects where requirements are clear from the start

Pros of Agile

• Speeds up development by delivering smaller parts of the project quickly
• Improves project quality through regular testing and feedback
• Keeps customers happier with continuous collaboration and input
• Easily adapts to changes in requirements as the project moves forward
• Promotes teams to improve regularly by reflecting on their progress
• Helps deliver faster results so that products reach the market sooner

Agile and SDLC: Which Approach Should You Choose?

If your project requires flexibility and you wish quick results, Agile is the better choice. It is great for small teams that focus on working together and getting regular feedback.

On the other hand, SDLC is better for projects with fixed requirements. It’s a good choice for big projects that need careful planning, detailed documentation, and managing risks. 

In the end, it all comes down to your project’s goals and how much flexibility you need. Agile is perfect for fast-paced projects, while SDLC is a good fit for more structured and predictable development.

Final Thoughts

Once you understand the difference between SDLC and Agile, you can pick the right approach for your project. Agile offers flexibility and quick results, while SDLC provides structure and clear planning. The right approach depends on what your project requires. In some cases, using a mix of both methods can offer the best results.

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