FlexSim uses object-oriented SEO as its software structure. FlexSim objects  are defined and programmed in four classes: fixed resource class, task executer class, node class and visual object class.
Drag and Drop Controls.
Users can build the model by dragging and dropping the abstracted, predefined 3D objects from different classes to layout, link and functionalize the model. For the senior users, the entire dragging and dropping procedures can be realized and the object parameters and behaviors can be modified using both FlexScript and C++ programming languages.
The "ExpertFit" Distribution-fitting software was developed by Dr. Averill M. Law, who is widely recognized as one of the world's foremost authorities on simulation and distribution fitting.