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

🔑 What It Is

• Written material describing a system: requirements, design, code, usage, maintenance.
• Produced alongside development, not bolted on after.

📌 Two Broad Categories

• Process documentation — plans, schedules, meeting minutes, standards, test plans. For dev team/PMs.
• Product documentation:
  • System documentation — spec, design docs, code comments, test docs → for developers/maintainers.
  • User documentation — manuals, install guides, help systems → for end users.

📌 Why It Matters for Maintenance

• Maintenance = 60–80% of lifetime cost (see System Delivery and Maintenance page).
• Good docs = maintainer can understand & safely change system they didn't build.
• Poor docs = direct cause of "lost context" problem.

⚠️ MCQ Trap

• A user manual = product/user documentation, NOT process documentation — even though written during the process. Category = what it describes, not when written.