print("hello world")printf("hello world");system.out.println("hello world");cout<<"HelloWorld\n";<?
each "HelloWorld";
?><!DOCTYPE html>
<html >
<head>
<meta charset="UTF-8">
<title> helloworld</title>
</head>
<body>
helloworld
</body>
</html><script type="text/javascript">
document.write("Hello World!");
</script>原文：https://www.cnblogs.com/swff/p/12359434.html