Hello, world!

#include <iostream>

int main()
{
    std::cout << "Hello, world!\n";
}

Actually, as of C++-23 this is no longer the best example of hello world. The way we write this canonical introduction has been superseded. The above form has been how every developer has learned to write this in C++ for more than 37 years. Now, the canonical example has transformed in to the following:

import std;

int main()
{
    std::println("Hello, world");
}

This is result of modularizing the standard library (p2465) and also creating a new formatted output library in the form of std::print (p2093 and p2539).