The class IlvSystemPort defines a rectangular area in which the user can draw. It can be either a real  place or a virtual  place. In the first case, the user draws directly into a region of the screen of the workstation. In the second case, the user draws into a bitmap in memory. The classes IlvBitmap and IlvAbstractView are derived from IlvSystemPort to accommodate these two possibilities. The IlvBitmap class is described later in this chapter. The IlvAbstractView class and its subclasses are described in the next chapter.