In professional SDLC practice, at what stages should documentation be prepared and updated for an information system?

Introduction / Context:
Documentation is the connective tissue of a project: it preserves decisions, enables onboarding, supports audits, and reduces knowledge risk. Good teams document continuously, not just at the end.

Given Data / Assumptions:

• Project follows an SDLC (analysis, design, build, test, deploy, operate).
• Question asks the appropriate timing for documentation.

Concept / Approach:
Each phase yields different artifacts: analysis (requirements, DFDs), design (architectures, structure charts), development (code comments, APIs), testing (plans, cases, results), deployment (run-books), and operations (SOPs, SLAs). Keeping documents current across all stages ensures traceability.

Step-by-Step Solution:

Verification / Alternative check:
Quality standards (e.g., ISO-style audits) require evidence across the lifecycle, not only at design or development.

Why Other Options Are Wrong:
Restricting documentation to analysis, design, or development creates gaps, undermining maintainability and compliance.

Common Pitfalls:
Letting documents drift after changes; avoid by integrating docs into the Definition of Done and using version control.

Final Answer:
at every stage