输出"Hello World!".

C语言:

#include <stdio.h>
int main() {
    printf("Hello World!\n");
    return 0;
}

C++:

#include <iostream>
using namespace std;
int main() {
    cout << "Hello World!" << endl;
    return 0;
}

Java:

public class Main {
    public static void main(String args[]) {
        System.out.println("Hello World!");
    }
}

Python3:

print('Hello World!')