COBOL Code Debug & Update

I have a compact COBOL module that needs a seasoned eye. The program is running but shows several logic and data-handling issues, and I’d like to take this opportunity to clean up the structure, add clear in-line comments, and make sure unit tests pass reliably.

You’ll be free to lean on tools such as ChatGPT, Claude, or any other AI assistant for brainstorming or quick pattern checks, but every line that goes into the final source must be reviewed and validated by you. Accuracy and clarity are more important than speed.

What I need from you
• Analyse the existing source, pinpoint the weak spots, and propose improvements
• Implement and debug the changes, compiling cleanly with no new warnings
• Run your own tests to confirm both functional behaviour and edge-case handling
• Provide a concise change log that explains what was modified and why (plain text or Markdown is fine)

Please include a brief note on your COBOL background—versions you’ve worked with, the typical environments you code for, and one example that highlights your debugging skills. Attach or link to any non-proprietary code samples if possible.

If this first round goes smoothly, I have a handful of similar COBOL maintenance tasks lined up and would be happy to keep collaborating.