## Contents

- Basic description and functionalities
- Adding a user subsection to an observation
  - Example
  - Detailed API
- Reading a user section from an observation
- Adding hooks to the Class commands
  - User hook for command DUMP
  - User hook for command SET VARIABLE USER
  - User hook for command FIND
  - API summary
- Extending the standard CLASS capabilities
- Backward compatibility
- Portability
- Conclusion
- Implementation details for CLASS developers