A Detailed Guide to the Phases, Processes, and Models of the Software Development Life Cycle (SDLC)

What is the Software Development Life Cycle (SDLC)? 

The Software Development Life Cycle (SDLC) is like a roadmap for making software. It shows all the steps from coming up with an idea to getting the software ready and keeping it working.

SDLC covers everything in the software journey, like planning, making, checking, and putting the software out there for people to use.

Process of the Software Development Life Cycle

• SDLC is like a plan for making software that's really good. It has all the steps from the beginning to when the software is no longer used.

  Using the SDLC plan makes sure the software is made in an organized and proper way.

• Reason:

• The main aim of SDLC is to make really good software that the customer wants. SDLC breaks this into steps like figuring out what's needed, making plans, writing code, checking everything works, and keeping it running. It's super important to do these steps in the right order to get things done well.

  Think about a team building software together. If each person does their own thing without talking to each other, like one person drawing, another writing code, and another doing paperwork, the project might not work out. So, it's important for the team to know what they're doing and work together to make the software just right.

• SDLC Cycle

The SDLC Cycle shows how software is made.
Look at this picture that shows how software is made:

Phases of the SDLC

• Listed below are the different stages:
• • Requirement gathering and analysis
  • Design
  • Implementation or coding
  • Testing
  • Deployment
  • Maintenance

1) Requirement Gathering and Analysis

In this step, we talk to the customer to find out exactly what they want their product to be like. We want to make sure we understand everything, so we ask a lot of questions.


The people in charge, like the business analyst and project manager, have a meeting with the customer. They talk about what the customer wants to make, who will use it, and what it will do. Before we start making anything, it's super important to know all about the product.


For example, if a customer wants an app for money stuff, we need to know all the details. Like, what kind of money things it will do, how they will work, and what money it will use.


Once we know everything, we check if it's possible to make the product. If there are things we're not sure about, we talk more to figure them out.


After we all understand what's needed, we make a special document called the Software Requirement Specification (SRS). The people who make the software read this document, and the customer looks at it too for later reference.




2) Design

During this stage, we use the information from the SRS document to make a plan for building the software. It's kind of like drawing a map before going on a big journey.


Here's a simpler explanation:


Using SRS Information: We take all the details from the SRS document, which tells us what the software should do. This becomes the starting point for our plan.


Creating the Software Plan: We make a detailed plan for how the software will be made. It's a bit like deciding on the materials and structure for a building. This includes picking the tools and methods we'll use and how information will flow within the software.


In short, the design phase is when we figure out how to build the software based on what the customer wants. It's like making a map before going on a trip to make sure everything goes smoothly.




3) Implementation or Coding

Once the developer has the design plan, they start building the software. This means they take the design and turn it into the real computer code. It's in this step that all the different pieces of the software are created.




4) Testing

After we finish writing the software, it's time to check if it works properly. We look at it really closely to find any mistakes or issues. If we find any problems, we let the developers know, and they fix them.


We keep testing it over and over until it works exactly the way the customer wants it to. To be sure it matches what the customer wants, we go back to the SRS document, which tells us what the customer expects.




5) Deployment

Once we're sure the software is good to go, we use it for real. There are two ways to do this. We either put it directly into the real working environment, or we let a group of users try it out first, depending on what the customer prefers.


If we use the user testing method (UAT), we create a copy of the real environment and let the customers and developers try it. If everything works as expected and everyone is happy, the customer says it's okay to make it available for everyone to use.




6) Maintenance

After we start using the software for real, we don't abandon it. We look after it. That means if there are any issues that pop up and need fixing or if we want to make it even better by adding new stuff, the developers are ready to help.

Evolution:

The story of Software Development Life Cycle (SDLC) is like a journey showing how making computer programs has changed over time. Here's a simple version:


1950s - 1960s: The Start


People just began to figure out how to make software when computers appeared.
They didn't have strict rules or plans, and they worked on computers with only a little paperwork.

1970s: Waterfall Model Begins


The Waterfall Model was born and became one of the first ways to make software.
It followed a step-by-step process where each part (like figuring out what's needed, designing, coding, testing) happened one after the other.


1980s: Smaller Steps


In the 1980s, they started breaking projects into smaller pieces and worked on them step by step.


1990s: Rapid Application Development (RAD)


The RAD model focused on quickly building software by creating early versions.
It was all about involving the people who would use the software and making things faster.


Late 1990s - Early 2000s: Agile Way


In the late 1990s, the Agile Manifesto came along. It brought a more flexible and customer-friendly approach.
Agile methods like Scrum and Extreme Programming (XP) became popular. They were about working together, adapting, and making working software in short bursts.


2000s: Lean and DevOps


In the 2000s, they started using Lean ideas to make software by being efficient and cutting waste.
They also introduced DevOps, which meant the development and IT teams worked together to make software better.


2010s - Present: Fast and Automated

Nowadays, they use Continuous Integration and Continuous Delivery (CI/CD) to quickly test, put together, and release software.




Agile methods keep changing, and there are new ones like SAFe for bigger companies.

Future Trends: Smart Software and Easy Coding

In the future, they might use more smart computer help (AI) and tools that make coding easier.
Some folks are using low-code or no-code tools, so even people who aren't expert coders can join in making software.
Over time, SDLC changed to fit what people needed for their software projects. Today, groups pick the way to make software that fits their project the best.

Models of the Software Development Life Cycle

Think of a software life cycle model as a map that guides how software is created. Even though there can be different paths, they all lead to the same basic steps and actions.

1) Waterfall Model

The Waterfall model is one of the earliest methods used in software development. It's also known as the linear sequential model. In this model, each phase is like a stepping stone to the next one. We only move on to the next phase when the previous one is fully completed. Here's how it works: Requirement Gathering and Analysis: We start by collecting and analyzing all the requirements. Once we have a clear understanding, we freeze the requirements, and that becomes the starting point. System Design: With the frozen requirements in hand, we begin designing the system. This design phase creates important documents that the next phase, Implementation and coding, will use. Implementation and Coding: Now, we get to the actual coding part. The software is built based on the design created in the previous step. Testing: After coding, we thoroughly test the software to find any problems. If we discover any issues, we log them and fix them. We keep testing and retesting until the software works perfectly. Deployment: Once the testing is successful and the customer gives the green light, we move the software into production. It's ready for use by everyone. Maintenance: Even after deployment, if any issues crop up in the live environment, developers step in to fix them. This is all part of keeping the software running smoothly. The Waterfall model is a step-by-step approach, where each phase depends on the completion of the previous one.

• Advantages of the Waterfall Model:

• The Waterfall Model is easy to understand as it follows a step-by-step approach.
• It defines clear goals for each phase, making the project Less complex and more controllable.

• Disadvantages of the Waterfall Model:

• The Waterfall Model takes a long time and isn't suitable for quick projects since you must finish one phase before moving on.
• It's not great for projects with uncertain or changing requirements. This model assumes that requirements are crystal clear from the beginning, and changes later on can be expensive and impact every phase of the project.

2) V-Shaped Model

The V-Shaped Model is like the Verification and Validation Model. Here, checking and testing happen at the same time as development, side by side. It's a lot like the Waterfall Model, but it pays extra attention to planning and testing right from the start.

a) Verification Phase: (i) Requirement Analysis: In this phase, we gather and analyze all the information we need. To make sure everything is correct, we review the requirements. (ii) System Design: Once we know what we need, we design the system. This means planning how all the parts will fit together and making documents to explain it. (iii) High-Level Design: High-level design is like making a map that shows how different parts work together. (iv) Low-Level Design: Low-level design goes deeper into the details, like designing individual pieces. (v) Coding: Now, it's time to write the actual code for the software. b) Validation Phase: (i) Unit Testing: Unit testing means looking closely at each part using special tests we made during the detailed design phase. The people who wrote the code do this testing to find problems early.

(ii) Integration Testing:

Think of integration testing as checking if puzzle pieces fit together. It happens during the High-level Design phase, and testers, not developers, do this.

(iii) System Testing

System testing is like checking if a whole car works, not just its parts. We do this during the System Design phase.

(iv) Acceptance Testing

Acceptance testing is when the customer checks if everything is as they wanted, and it's done in their own environment.

Advantages of V-Model:

It's a simple and easy-to-understand way of doing things.

V-Model works well for smaller projects where the rules don't change much.

It's organized and strict, leading to top-notch results.

Disadvantages of V-Model:

V-Model isn't great for long, never-ending projects.

If the rules change later, it can get really expensive.

3) Prototype Model

The prototype model is like making a rough draft of the software before the final version. These drafts might not work perfectly and might have only basic functions. We use fake functions to create these drafts. It's a bit like showing the customer a rough sketch to figure out their preferences. We make these software drafts to get feedback from the customer. They tell us what they do and don't like. We make changes based on their input and keep showing them until they're pleased. We repeat this process until the customer is happy with the draft.

Once we've gathered what the customer wants, we make a quick draft and show it to them. We listen to what the customer says and make the draft better based on their feedback. We do this over and over until the customer is happy with it. Once they say it's good to go, we use it as the plan to build the real software using the Waterfall method. Advantages of Prototype Model:

• The prototype model saves time and money because we catch problems early on.
• If something is missing or needs to change, we figure it out during the review and fix it in the improved draft.
• Having the customer involved from the beginning avoids misunderstandings about what the software should do.

Disadvantages of Prototype Model:

• Because the customer is part of every step, they might want to change the final product. This can make the project more complicated and take longer to finish.

4) Spiral Model

The Spiral Model is like a mix of trying things out and making improvements. It goes in circles, like a spiral. Each circle goes through different steps of building software. The innermost loop starts by figuring out what's required and creating a plan for how to do it. Then, it checks for risks, creates, tests, and looks at what's been done. The next circle handles designing, making it, and testing it all over again. The Spiral Model has four main steps: Planning Risk Analysis Engineering Evaluation

(i) Planning:

Planning is all about gathering information from the customer and writing it down. We use this information to create a document called the Software Requirement Specification for the next step.

(ii) Risk Analysis:

In this phase, we deal with potential problems. We pick the best way to solve these problems and try them out with a prototype. For example, if we're worried that getting data from a faraway database will be too slow, we test it with a prototype.

(iii) Engineering:

After dealing with risks, we start building and testing.

(iv) Evaluation:

The customer checks what we've made and decides what to do next.

Advantages of Spiral Model:

• We look closely at risks with prototypes.
• We can make things better or change them in the next round.

Disadvantages of Spiral Model:

• This model works best for big projects.
• It can take a long time and be expensive because it might need lots of rounds to finish the product.

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• 5) Iterative Incremental Model 

• The iterative incremental model breaks the product into small parts.

  For example, we decide on a feature to work on in each part. Each part goes through phases like Requirement Analysis, Designing, Coding, and Testing. We don't need detailed planning for each part.

  Once a part is done, we check it and give it to the customer for feedback. We take the customer's feedback and use it in the next part, along with adding new features.

  This way, the product grows with more features. When we finish all the parts, the final product has everything.

  Phases of Iterative & Incremental Development Model:

  1. Inception Phase: This is where we gather the requirements and understand what the project is about.

  2. Elaboration Phase: We create the basic architecture of the product and address any risks we found in the inception phase. We also make sure the non-functional requirements are met.

  3. Construction Phase: Here, we fill in the architecture with actual code. It's ready to be used and goes through analysis, design, coding, and testing to make sure it does what it's supposed to do.

  4. Transition Phase: This is when we put the product into the real working environment.

  Advantages of Iterative & Incremental Model:

  • It's easy to make changes to the requirements, and it won't cost much because we can include them in the next part.
  • We look at risks and find problems early in each part.
  • We catch defects early too.
  • Breaking the product into small parts makes it easier to manage.

  Disadvantages of Iterative & Incremental Model:

• You need to fully understand the product to break it down and build it incrementally.

• 6) Big Bang Model

• The Big Bang Model is a bit like making a surprise gift. You gather some money and resources and start creating a product. The final product may or may not be exactly what the customer wanted.

  With this model, you don't need to plan too much or make schedules. The developer simply analyzes the requirements, writes the code, and builds the product based on their own understanding. It's mainly used for small projects, and there's no formal testing team involved. This lack of testing can lead to project failures.

  Advantages of the Big Bang Model:

  • It's a very simple and straightforward approach.
  • You don't need extensive planning or schedules.
  • Developers have the freedom to create the software as they see fit.

  Disadvantages of the Big Bang Model:

• It's not suitable for large, ongoing, or complex projects.
• There's a high level of risk and uncertainty because you're not following a structured process.

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• 7) Agile Model

• The Agile Model is similar to constructing something with building blocks. Instead of attempting to complete the entire structure all at once, we build it gradually by adding more components as we progress. In Agile, we divide the product into tiny parts called incremental builds. We don't try to build the whole product from the start. Instead, we start with a basic version and add more features in each build. Each new build is like a building block, using what we've already created. In Agile, we work in short bursts called sprints, which last 2-4 weeks. At the end of each sprint, the product owner checks it. Once they say it's good, we give it to the customer. We really care about what the customer thinks. They give us feedback, and we use their suggestions to make the next sprint even better. We also do testing in each sprint to make sure everything works smoothly and avoid any problems.
• 

  
  

  Advantages of Agile Model:

  1. Flexibility: Agile can easily adjust to changes.
  2. Adding Features: It's simple to add new features.
  3. Customer Satisfaction: Regular feedback and suggestions make customers happier.

  Disadvantages:

  1. Less Documentation: Agile tends to have less formal documentation.
  2. Skilled Team Needed: You need experienced and skilled team members.
  3. Clear Vision Required: If the customer isn't sure what they want, the project can be tricky.

  4. 
     

  1. Conclusion

  1. Choosing the right software development life cycle is crucial for successfully completing a project and making management more manageable.

     Various software development life cycle models come with their own advantages and disadvantages. The best model for a particular project depends on factors like clear or unclear requirements, system complexity, project size, cost, available skills, and more.

     For instance, when dealing with unclear requirements, Spiral and Agile models are ideal because they allow for easy adjustments at any stage.

     It's worth noting that the Waterfall model serves as the foundation for all other SDLC models.

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  waterfall model