Selecting buttons with keyboard Possible Duplicate:
  How can I select buttons with just the keyboard?  




I have been using OS X for only a while now and am finding certain things a bit hard to do. Consider an option box shown below :-


Pressing an enter key would shut down the system, however how do I select the "restart" or the "cancel" options using they keyboard alone? Whats the keyboard shortcut for that? Arrow keys just dont work.
Coming from a Linux/Windows background, this is really confusing.
Use the Tab key to switch buttons then return to activate that. 

I think all GUIs I have used - Windows, OS X, X11, old Mac all have this.