Applications
As of 2007, most business applications are intended to run on platforms with virtual memory. A developer on such a platform can design a program as if the memory constraint does not exist unless the program's working set exceeds the available physical memory. Most importantly, the architect can focus on the problem being solved without the added design difficulty of forcing the processing into steps constrained by the overlay size. Thus, the designer can use higher-level programming languages that do not allow the programmer much control over size (e.g. Java, C++, Smalltalk).
Still, overlays remain useful in embedded systems. Some low-cost processors used in embedded systems do not provide a memory management unit (MMU). In addition many embedded systems are real-time systems and overlays provide more determinate response-time than paging. For example the Space Shuttle Primary Avionics System Software (PASS) uses programmed overlays.
Even on platforms with virtual memory, software components such as codecs may be decoupled to the point where they can be loaded in and out as needed.
Read more about this topic: Overlay (programming)