CSS CS Optional — Paper-I, Section-B, Topic V.

🔑 Definition

• Change is continuous and inevitable, not just corrective.
• Broader lens; maintenance = day-to-day activity within it.

📌 Lehman's Laws (name 2)

• Continuing Change — active system must keep changing, or it becomes less useful.
• Increasing Complexity — structure gets more complex unless work is done to reduce it.

📌 Staged Model (full lifecycle)

1. Initial development — first working version
2. Evolution — active feature/adaptation period
3. Servicing — minor fixes only, no new development
4. Phase-out — system withdrawn, replaced

⚠️ MCQ Trap

• Evolution = broad, continuous-change lens across whole life.
• Maintenance = day-to-day corrective/adaptive/perfective/preventive activity.
• Not interchangeable synonyms in a "distinguish" question.