namespace

e.g.1

#include <iostream>

int main(void)
{
    
    std::cout << "Hello, world!" << std::endl;
    return 0;
}

e.g.2

#include <iostream>

using namespace std;

int main(void)
{
    
    cout << "Hello, world!" << endl;
    return 0;
}

–ß‚é