In section 6.4 of Code Complete 2nd Edition there is a paragraph about hiding global data. What I am particularly interested in, is that McConnell (the author of the book) gives examples of the benefits of hiding global data. There is one example that I cannot understand. I don't have the English version of the book, so I'll try to translate the text.
Hiding global data. (...) You can change the structure of the data without modifying the program.
What does McConnell mean by that? Is he talking about changing global data? If so, why wouldn't you have to modify your program when you are using methods to retreive that data? Or maybe he is referring to something else here?
I would greatly appreciate if someone could clear up my confusion. If you could also provide an example, it would be great (examples are awesome, you know).