What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners! [closed]

Question

Enter this code in your address bar (in your browser) and press enter. Then you can edit all the content of the webpage!

javascript:document.body.contentEditable='true'; document.designMode='on'; void 0

That is the coolest "one-liner" I know =)

When I first wrote this.

10 PRINT "What is your name?"
20 INPUT A$
30 PRINT "Hello " A$
40 GOTO 30

It blew people away! The computer remembered their name!

EDIT: Just to add to this. If you can convince a new programmer this is the coolest thing they can do, they will become the good programmers. These days, you can do almost anything you want with one line of code to run a library somebody else wrote. I personally get absolutely no satisfaction from doing that and see little benefit in teaching it.

PHP - the Sierpinski gasket a.k.a the Triforce

OK, it's 15 lines of code but the result is awesome! That's the kind of stuff that made me freak out when I was a child. This is from the PHP manual:

$x = 200;
$y = 200;

$gd = imagecreatetruecolor($x, $y);
 
$corners[0] = array('x' => 100, 'y' =>  10);
$corners[1] = array('x' =>   0, 'y' => 190);
$corners[2] = array('x' => 200, 'y' => 190);

$red = imagecolorallocate($gd, 255, 0, 0); 

for ($i = 0; $i < 100000; $i++) {
  imagesetpixel($gd, round($x),round($y), $red);
  $a = rand(0, 2);
  $x = ($x + $corners[$a]['x']) / 2;
  $y = ($y + $corners[$a]['y']) / 2;
}
 
header('Content-Type: image/png');
imagepng($gd);

Microsoft has Small Basic, an IDE for "kids".

pic = Flickr.GetRandomPicture("beach")
Desktop.SetWallpaper(pic)

It is specifically designed to show how cool programming is.

I tend to think that people are impressed with stuff that they can relate to or is relevant to their lives. I'd try and base my 10 lines of code around something that they know and understand. Take, for example, Twitter and its API. Why not use this API to build something that's cool. The following 10 lines of code will return the "public timeline" from Twitter and display it in a console application...

using (var xmlr = XmlReader.Create("http://twitter.com/statuses/public_timeline.rss"))
    {
        SyndicationFeed
            .Load(xmlr)
            .GetRss20Formatter()
            .Feed
            .Items        
            .ToList()
            .ForEach( x => Console.WriteLine(x.Title.Text));
    }

My code sample might not be the best for your students. It's written in C# and uses .NET 3.5. So if you're going to teach them PHP, Java, or C++ this won't be useful. However, my point is that by associating your 10 lines of code with something "cool, interesting, and relevant to the students your sample also becomes cool, interesting, and relevant.

Good luck!

[Yes, I know that I've missed out a few lines of using statements and the Main method, but I'm guessing that the 10 lines didn't need to be literally 10 lines]

This is a Python telnet server that will ask for the users name and say hello to them. This looks cool because you are communicating with your program from a different computer over the network.

from socket import *
s=socket(AF_INET, SOCK_STREAM)
s.bind(("", 3333))
s.listen(5)
while 1:
   (c, a) = s.accept()
   c.send("What is your name? ")
   name = c.recv(100)
   c.send("Hello "+name)
   c.close()

I got a great response from my kids with a quick VB script to manipulate a Microsoft Agent character. For those that aren't familiar with MS Agent, it's a series of animated onscreen characters that can be manipulated via a COM interface. You can download the code and characters at the Microsoft Agent download page.

The folllowing few lines will make the Merlin character appear on screen, fly around, knock on the screen to get your attention, and say hello.

agentName = "Merlin"
agentPath = "c:\windows\msagent\chars\" & agentName & ".acs"
Set agent = CreateObject("Agent.Control.2")

agent.Connected = TRUE
agent.Characters.Load agentName, agentPath
Set character = agent.Characters.Character(agentName)

character.Show

character.MoveTo 500, 400
character.Play "GetAttention"
character.Speak "Hello, how are you?"
Wscript.Sleep 15000
character.Stop
character.Play "Hide"

There are a great many other commands you can use. Check http://www.microsoft.com/technet/scriptcenter/funzone/agent.mspx for more information.

EDIT 2011-09-02 I recently discovered that Microsoft Agent is not natively installed on Windows 7. However it is offered as a separate download here. I have not tested this so cannot verify whether it operates.