c++ header example

Example 1: what is a header in c++

// my_class.h
#ifndef MY_CLASS_H // include guard
#define MY_CLASS_H

namespace N
{
    class my_class
    {
    public:
        void do_something();
    };
}

#endif /* MY_CLASS_H */

Example 2: what is a header in c++

// my_class.cpp
#include "my_class.h" // header in local directory
#include <iostream> // header in standard library

using namespace N;
using namespace std;

void my_class::do_something()
{
    cout << "Doing something!" << endl;
}

Example 3: what is a header in c++

// my_class.h
namespace N
{
    class my_class
    {
    public:
        void do_something();
    };

}

Example 4: c++ header files example

//headers 
#ifndef TOOLS_hpp 
#define TOOLS_hpp
#include<vector> 
#include<iostream>
#include<fstream>
#include<string>
using std::ifstream;
using std::cout; 
using std::cin;
using std::endl;
using std::cerr;
using std::vector;
using std::string;
// functions prototypes 
inline vector<int> merge(const vector<int>&a,const vector<int>& b);//merge function prototype with Formal Parameters 
std::vector<int> sort(size_t start, size_t length, const std::vector<int>& vec);//sort function prototype with formal parameters 
#endif