The plug-in modules shown in the figure work in concert with custom code to operate a working system. By sharing and re-using substantial chunks of code, we can shorten the development cycle for robot software while improving the robustness and reliability of the finished product. It's no accident that the first module written for the Rossum Project was the RP1 robot simulator. It has an important role to play in this open-source robotics software project. One of the things that makes it so hard to write software for robots is that there is no common platform.
Robots are very specialized devices and no two systems are alike.
You can download robot software from the web, but you can't download the robot to run it. The RP1 simulator gives you an opportunity to find out. Second, it provides a way for software developers to demonstrate their components. When you download a module that can run on the simulator, you have a pretty good idea how it operates, what it does, and of whether it will meet your needs. You will have seen the the thing actually work .