The beginning of Chapter 3, “Dealing with Data,” mentions three fundamental properties of which a computer program must keep track when it stores data. To save the book the wear and tear of your thumbing back to that chapter, here are those properties again:
Where the information is stored
What value is kept there
What kind of information is stored
You've used one strategy for accomplishing these ends: defining a simple variable. The declaration statement provides the type and a symbolic name for the value. It also causes the program to allocate memory for the value and to keep track of the location internally.
Let's look at a second strategy now, one that becomes particularly important in developing C++ classes. This ...