title: What's the difference between a string constant and a string literal?
body: <p>I'm learning objective-C and Cocoa and have come across this statement:</p>
  
  <blockquote>
    <p>The Cocoa frameworks expect that global string constants rather than string literals are used for dictionary keys, notification and exception names, and some method parameters that take strings.</p>
  </blockquote>
  
  <p>I've only worked in higher level languages so have never had to consider the details of strings that much. What's the difference between a string constant and string literal?</p>