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The Software Development Life Cycle (SDLC) isn't just a checklist developers follow—it's a framework for understanding how complex systems move from idea to reality. You're being tested on your ability to recognize why each stage exists, what problems it solves, and how skipping or poorly executing a stage creates downstream failures. The SDLC demonstrates core principles of iterative design, abstraction, and systematic problem-solving that appear throughout AP coursework.
When you encounter questions about software development, think beyond "what happens when." Focus on the relationships between stages: how requirements shape design, how design constrains implementation, and how testing validates everything that came before. Don't just memorize the stage names—know what concept each stage illustrates and be ready to explain why the order matters.
Before any code gets written, developers must understand what they're building and why. These early stages prevent the most expensive mistakes—building the wrong thing entirely.
Compare: Requirements Gathering vs. Design—both happen before coding, but requirements define what the system should do while design defines how it will do it. If an FRQ asks about project failures, trace back to which of these stages was inadequate.
These stages transform abstract plans into working software, then verify that what was built matches what was planned. The gap between design and reality is where most bugs are born.
Compare: Implementation vs. Testing—implementation asks "does it run?" while testing asks "does it run correctly?" Strong exam answers recognize that testing isn't just finding bugs; it's verifying that requirements were actually met.
Software isn't finished when it works—it's finished when users can actually use it, and even then it continues to evolve. Most software spends far more time in maintenance than in initial development.
Compare: Deployment vs. Maintenance—deployment is a moment (releasing the software), while maintenance is ongoing (keeping it running). Exam questions often test whether students understand that maintenance typically consumes 60-80% of total software costs.
| Concept | Best Examples |
|---|---|
| Understanding user needs | Requirements Gathering, UAT (in Testing) |
| Planning before building | Requirements Gathering, Design |
| Abstraction and blueprints | Design (architecture, patterns) |
| Translating plans to reality | Implementation |
| Quality assurance | Testing, Code Reviews (in Implementation) |
| Risk management | Phased Deployment, Feasibility Analysis |
| Iterative improvement | Maintenance, Requirements updates |
| Documentation importance | All stages—especially Deployment and Maintenance |
Which two SDLC stages are most focused on understanding what should be built rather than how to build it?
A software team released an application that works perfectly but users find it confusing and slow. Which stages likely had inadequate attention, and why?
Compare and contrast unit testing and user acceptance testing—what does each validate, and why are both necessary?
If a company skips the Design stage and moves directly from Requirements to Implementation, what types of problems would you predict? Connect your answer to the concept of abstraction.
An FRQ describes a software project where bugs discovered after deployment cost 10x more to fix than bugs found during development. Which SDLC stages could reduce this cost multiplier, and how?