Question

I am learning about C++ classes and I realized that if I tried to move my class declaration and definition of class Date from main.cpp to another c++ file, say test.cpp and compiled the two files I got an error saying Date was not declared. Why is that?

Answer 1

This is why you have header files. You need a header file test.h that contains only the class definition (that is mostly function declarations) and test.cpp that contains the actual function definitions (the code).

In main.cpp you’ll have to #include "test.h".