This illustrates writing simple classes (using just types like strings and arrays; there are no container classes like vector or map) in a multi-file project. Files:
phonebook.h: classes for
tracking phone numbers
phonebook.cpp:
implementation of the phonebook class (the entry class is all inline)
main.cpp: test bed
Makefile: build file for
command-line make (using g++). You can also
build the code in CLion or by typing g++ *.cpp