how to write hello world in c 2b 2b

1#include <iostream>
2
3
4int main(){
5 std::cout <<"Hello World" << std::endl;
6 return 0;
7}
8

1#include<iostream>
2using namespace std;
3
4int main(){
5 
6  cout << "Hello World" << endl;
7  
8  return 0;
9}

1#include <iostream>
2//optional using namespace std;
3int main() {
4    std::cout << "Hello, World!" << std::endl;
5    return 0;
6}
7