- forgetting to declare the function before calling it
- not including the header file
- not declaring the function in the header file
- not implementing the function
- the .cpp file with the function is not getting linked with your main file
These are some of the possible errors that can happen when we start working with more moving parts. As a beginner it is good to actually try and do them deliberately and see what errors we are getting, so the next time you see that error in your code, you'd have an idea of what went wrong.
Please leave out comments with anything you don't understand or would like for me to improve upon.
Thanks for reading!