Software for embedded systems typically have a small footprint (i.e. be able to run in a small amount of memory) and often has to work in real-time . Specialised operating systems and languages facilitate the production of real-time software with a small footprint: only the modules required in a specific system will be included. The development environment should include facilities for testing and debugging the software. Emulators can be used to test the software without the target system (especially useful if the target system is not yet available) and related equipment (such as machine tools).