C++ Header File (.h)

A header file (.h) defines the interface to the class, which includes:

• Declaration of all member values.
• Declaration of all member functions.

cpp-class/Cube.h

#pragma once            // << Compile once

class Cube {            // << Class name
	public:
		double getVolume();              // << Public variable
		double getSurfaceArea();
		void setLength(double length);   // << Public method
		
	private:
		double length_;                  // << Private variable
};

The #pragma once line is always present on .h files and tells the compiler to compiles this file once regardless of how many programs user the header.

The class Cube line tells the compiler to create a new class called Cube, with both public and private methods and variables.