To support virtual functions $($i$.$e$.,$ shape functions that can either refer to rectangle functions or triangle functions$),$ we use what's known as a virtual function pointer table that contains function pointers that refer to the correct functions. For example, rectangle$\_$t will have function pointers within the shape$\_$t portion that point to rectangle functions, and triangle$\_$t will have function pointers within the shape$\_$t portion that point to triangle functions. Thus, a shape can call the appropriate function by using the virtual function pointer table. For example, the provided shape$\_$area function uses the table to call the appropriate area function for the shape.