• Certain program options are either mutually exclusive or not always accessible. This
is easiest to visualize in menu-driven programs. For example, an application program
may give the user several menu choices as shown in Figure 3.4. The system
allows the operator to make only one selection at a time. If the user selects the first
option then the module with the program instructions to move records to the file is
the only one that is being used, so that is the only module that needs to be in memory
at this time. The other modules all remain in secondary storage until they are
called from the menu.