Topic 1 · System Fundamentals

Hardware = physical (chip, screen). Software = invisible instructions (app, OS).

Planning → Analysis → Design → Implementation → Testing → Deployment → Maintenance. Memory: P-A-D-I-T-D-M.

Feasibility study, rough budget, risks. Cheapest stage — biggest leverage.

Capture requirements from real stakeholders. Skipping this = building the wrong thing.

Architecture diagrams + UI mockups + data models. Fixing a flaw here is 10–100× cheaper than fixing it after launch.

Actual coding. Usually only ~30% of total project time.

Unit → Integration → System → User Acceptance Testing (UAT). UAT = real users approve.

Move new system live + migrate data + train users + plan rollback.

Corrective (bugs), Adaptive (env changes), Perfective (new features), Preventive (tidy code). Usually >50% of lifetime cost.

Linear, doc-heavy; each stage finishes before next. Best for stable + regulated (medical, aerospace).

Short sprints; working code each cycle. Best for uncertain + fast-feedback (apps, startups).

Most real projects mix both — Agile day-to-day, Waterfall for major releases.

Adding people to a late project makes it later. Communication overhead explodes.

Implementation ≠ Deployment. Implementation = coding; Deployment = rolling out.