Now select the problematic application from the list – which will often have a message next to it – and click the blue Force Quit button. The Mac doesn’t have a delete key, meaning the time honoured Ctrl-Alt-Del combination won’t work, so use instead Cmd-Alt-Esc to bring up the Force Quit window.
OSX is a very stable system but from time to time an application may stop responding, requiring you to manually shut it down. Mountain Lion does have a maximise feature though, for most apps, that’s engaged by clicking on the two grey arrows in the upper right corner of the window. Instead it’s enlarged to a size that fits the information on the page. The yellow minus does minimize the app exactly as Windows does, but the green plus button doesn’t maximise the pane. Clicking the red cross will close the current window, but not the app itself. The traffic light buttons in the top left of the pane look similar to Windows, but they behave differently. The way windows function on OSX can be a little bewildering at first for long-time PC users.