The most complex use of 32-bit memory involves placing the primary control of the program in a 32-bit code segment. In this type of application, the USE16 segment is reduced to helper status exclusively. During initialization, the USE16 segment allocates the 32-bit memory for code and data, loads the code into the USE32 segment, creates a code-segment alias for the USE32 segment, and then calls the main entry point in the USE32 segment.
From then on, the USE32 segment takes control of the program, calling into the USE16 helper segment only when the application needs to call Windows or MS-DOS functions. The USE32 segment continues to control the flow of the program until the application is ready to close. Only then does it return control to the USE16 segment so the USE16 segment can free the 32-bit memory and perform other cleanup tasks before the application quits.