Slight clarification in chapter 2

Closes marijnh#175

Author: marijnh

02_program_structure.txt

@@ -559,7 +559,8 @@ console.log(name);
 force you to enter a name. It will ask again and again until it gets
 something that is not an empty string. Applying the `!` operator will
 convert a value to Boolean type before negating it, and all strings
-except `""` convert to `true`.
+except `""` convert to `true`. This means the loop continues going round
+until you provide a name that is not the empty string.
 
 == Indenting Code ==