🔄 How Is Software Built?

Systems Development Life Cycle (SDLC)

Building software isn't just writing code. There's a whole process — from understanding what the user wants, to testing, launching and maintaining. Different teams use different approaches.

DigiTech A-Level §2.1.3 CS GCSE §1.7

🤔 Why can't you just start coding?

Imagine building a house without plans — you'd end up with doors that don't fit, rooms in wrong places, and a very unhappy customer. Software is the same. The SDLC is the plan that makes sure the right thing gets built, the right way.

📋

Choose a methodology

🏔️

Waterfall

🔄

Agile

🌀

Spiral

✅

V-Model

⚡

RAD

📊

Comparison Table

	🏔️ Waterfall	🔄 Agile	🌀 Spiral	✅ V-Model	⚡ RAD
Approach	Sequential	Iterative	Risk-driven	Sequential + testing	Prototype-driven
Flexibility	Low ❌	High ✅	Medium	Low ❌	High ✅
User involvement	Start & end only	Continuous ✅	At reviews	Start & end	Continuous ✅
Best for	Clear, fixed requirements	Changing requirements	High-risk, large projects	Safety-critical systems	Quick prototypes
Example	Bridge, building	App, website	Military, medical	Aircraft software	Startup MVP

📝 Exam tip: The exam usually asks you to recommend a methodology for a given scenario. Key question: "Do the requirements change?" If yes → Agile. If no → Waterfall. If high risk → Spiral. If safety-critical → V-Model.