Hello world

C++ :

#include <iostream>

using namespace std;

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

Rust :

fn main()
{
    println!("Hello world!");
}

The exclamation mark at the end of println! indicates this is a macro rather than a function. The println! macro is defined in rust standard library and is used to output to the console.