When running a 5-file + corresponding .h files that store prototypes for a project in C++ on VS Code, I get the following error message:

I was able to fix this error by including the cpp files, not just the headers, in my main file.

The purpose of my question is to gain insight on why this happens.

I tried to:

• Remove all uneccessary deconstructors (may have helped)
• Scan all files for syntax errors (none)
• looking for issues with finding files from main by renaming them (waste of time)