How Do You Exit A Game

i dont know the name of the code so that i can exit the game when i press the button yes here is my code:

 function OnGUI () {
 // Make a background box

GUI.Box (Rect (10,10,300,90), "Exit To Desktop?");

 // Make the first button. If it is pressed, Application.Loadlevel (1) will be executed
 if (GUI.Button (Rect (130,40,80,20), "Yeah")) {
 }
 }