title: writeToFile:atomically: what does atomically mean?
body: <p>I am wondering what the <code>atomically:</code> parameter stands for in the <code>writeToFile:atomically:</code> method (<code>-[NSArray writeToFile:atomically:]</code> for example). It is common to pass <code>YES</code> for <code>atomically:</code>, but I don't know what it means.</p>