Modifying the software by restructuring is called

Answer: Perfective maintenance

Explanation: Modifying software by restructuring (also called refactoring) to improve internal design, readability, maintainability, or performance without changing external behavior is an example of perfective maintenance.

Key differences between maintenance types:

• Perfective maintenance: Improves non-functional aspects and internal quality — includes restructuring or refactoring code.

• Corrective maintenance: Fixes defects and bugs so the software works as intended.

• Adaptive maintenance: Updates the software to remain compatible with changes in its environment (e.g., new OS, hardware, regulations).

• Preventive maintenance: Makes changes aimed at reducing the likelihood of future failures (e.g., adding tests, inspections).

Example: Rewriting a messy module to improve readability and reduce technical debt is perfective maintenance because it restructures the code without altering its outward behavior.