Waterfall Model

The Waterfall model follows the standard SDLC phases one after another, in a fixed sequence. Each phase has to be finished completely before the next one begins, and whatever comes out of one phase decides how the next one goes. Progress flows in one direction only, almost like water going downhill, through stages like requirements, design, building, testing, deployment, and maintenance.

Compared to newer approaches like Agile, it is one of the least flexible models since there is barely any room to loop back or adjust mid-way. It is also the oldest SDLC model out there. Back when it was first used, there was not really any other structured approach for this kind of work.

Waterfall Model: Step-by-Step Process

Step 1: Requirements Gathering

Collect and document all the project requirements before development begins.

Step 2: Design

Create the system design based on the approved requirements.

Step 3: Coding

Develop the software according to the design specifications.

Step 4: Testing

Test the completed software to identify and fix defects.

Step 5: Deployment

Release the software to the production environment for users.

Step 6: Maintenance

Provide ongoing support by fixing bugs, updating features, and making necessary improvements after deployment.

In the Waterfall model, each stage must be completed and approved before moving to the next stage. There is no jumping back and forth between phases once the project moves forward.

Advantages and Disadvantages

The biggest advantage is predictability. Since everything is planned upfront, it is easy to estimate timelines, costs, and resources. It also makes documentation thorough, since every requirement is written down before coding starts. The downside is flexibility, or the lack of it. If a requirement changes midway, or a problem is found in an earlier phase, fixing it means going back and redoing work, which costs time and money.

When to Use Waterfall

Waterfall works best for small to medium projects where the requirements are clear, well understood, and unlikely to change. It also suits projects with strict regulatory or compliance needs, where having detailed documentation at every step matters.