When you learn a new programming language, usually the first program you learn prints or outputs the text Hello World! As I learn more programming languages I will add to this post.

C++

#include <iostream>
using namespace std;

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

Not eXactly C (NXC)

task main() {
	TextOut(0, LCD_LINE1, "Hello World!");
	Wait(1000);
}

PHP

<?php

echo "Hello World!";

?>

JavaScript

document.write("Hello World!");
alert("Hello World!");

HTML

<p>Hello World!</p>

CSS

body:before{
	content: "Hello World!";
}

Next Byte Codes (NBC)

thread main
TextOut(0, LCD_LINE1, 'Hello World!')
wait SEC_10
endt

Batch file

@echo Hello World!
@pause

AutoHotKey

MsgBox Hello World!