20-sim is a modeling and simulation software developed by Controllab for the simulation of dynamic systems. It allows users to model systems using various formalisms such as block diagrams, bond graphs, and differential equations. The software provides tools for analyzing and designing control systems, with capabilities for real-time simulation and hardware-in-the-loop testing. It is widely used in the engineering field for designing mechanical, electrical, and hydraulic systems. Users can access a range of visualization tools and libraries to facilitate the simulation of complex systems.