.h files, or header files, serve as declarations for classes and functions in C++. They outline what a class does without detailing how it accomplishes those tasks. For instance, when creating a Circle class to calculate area, the header file will declare its methods but not implement them. This separation is crucial; it prevents multiple definitions during compilation by using preprocessor directives like #ifndef, #define, and #endif.
On the other hand, .cpp files are where the actual implementation happens. They include necessary headers at their beginning with an #include directive that brings in declarations from corresponding .h files. Continuing our Circle example, this file would define how to compute the area based on radius input.
This division between declaration (.h) and definition (.cpp) enhances code organization—especially vital as projects grow larger—and facilitates easier maintenance and readability. It allows programmers to focus on interfaces rather than implementations initially.
A common practice is naming these pairs consistently (e.g., Circle.h for declarations and Circle.cpp for definitions), which helps maintain clarity within your project structure.
When you compile your program, each .cpp file generates an object file (.obj), which gets linked together into an executable program. Understanding this process can demystify some complexities of C++ programming while reinforcing good coding practices.