Ordinarily, whenever you define a global variable, the C++ compiler allocates the memory required to hold an object corresponding to the variable's type, be it a built-in type, such as int, or a user-defined class, such as cylinder. In this chapter, you learn about an alternative whereby C++ allocates only a small amount of memory for a pointer at compile time, deferring until run time the allocation of memory for an object.

In the hardcopy version of this book, you learn that run-time allocation enables you to reduce the memory consumed by your program when the number of objects that your program encounters is less than your worst-case estimate of that number.