Waterfall model in Software Engineering - Step-by-Step Execution

Concept Flow - Waterfall model

Requirements

↓

Design

↓

Implementation

↓

Testing

↓

Deployment

↓

Maintenance

↓

END

The Waterfall model follows a step-by-step flow from Requirements to Maintenance, completing each phase fully before moving to the next.

Execution Sample

Software Engineering

Phase 1: Gather requirements
Phase 2: Design system
Phase 3: Write code
Phase 4: Test system
Phase 5: Deploy
Phase 6: Maintain

This sequence shows the Waterfall model phases executed one after another without overlap.

Analysis Table

Step	Phase	Action	Output	Next Phase
1	Requirements	Collect all user needs	Clear requirements document	Design
2	Design	Plan system architecture	Design specifications	Implementation
3	Implementation	Write and build code	Working software modules	Testing
4	Testing	Check for bugs and errors	Test reports and fixes	Deployment
5	Deployment	Release software to users	Software in production	Maintenance
6	Maintenance	Fix issues and update	Updated software	END

💡 All phases completed sequentially; no phase starts before previous finishes.

State Tracker

Phase	Status Start	After Completion
Requirements	Not started	Completed
Design	Not started	Completed
Implementation	Not started	Completed
Testing	Not started	Completed
Deployment	Not started	Completed
Maintenance	Not started	Ongoing or Completed

Key Insights - 3 Insights

Why can't we go back to a previous phase once it's done?

In the Waterfall model, each phase must finish completely before the next starts, so going back is not part of the process (see execution_table rows 1-6).

What happens if a problem is found during Testing?

Testing phase fixes issues before Deployment, but major changes require revisiting Implementation or Design, which is difficult in Waterfall (see execution_table row 4).

Is Maintenance part of the development or after release?

Maintenance happens after Deployment to fix bugs or update software while it is in use (see execution_table rows 5-6).

Visual Quiz - 3 Questions

Look at the execution_table, what is the output after the Design phase?

A Test reports and fixes

B Working software modules

C Design specifications

D Clear requirements document

💡 Hint

Check the Output column in row 2 of the execution_table.

At which step does the software get released to users?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look at the Phase and Action columns in the execution_table for deployment.

If a bug is found during Testing, which phase is responsible for fixing it before release?

A Testing

B Requirements

C Deployment

D Implementation

💡 Hint

Refer to the Action and Output in the Testing phase in the execution_table.

Concept Snapshot

Waterfall model is a linear software development process.
Phases: Requirements -> Design -> Implementation -> Testing -> Deployment -> Maintenance.
Each phase must finish before the next starts.
Changes are hard to make once a phase is complete.
Best for projects with clear, fixed requirements.

Full Transcript

The Waterfall model is a step-by-step approach to software development. It starts with gathering all requirements, then designing the system, followed by coding, testing, deploying, and finally maintaining the software. Each phase must be fully completed before moving on to the next. This model does not allow going back easily to previous phases. Testing finds bugs which are fixed before deployment. Maintenance happens after release to keep the software updated. This model works well when requirements are clear and unlikely to change.