EasyDyn: Easy Simulation of Dynamic Problems. EasyDynDyn is a C++ library for the simulation of problems represented by second-order (or first-order) differential equations and, more particularly, multibody systems. The library is free and distributed under the GPL. To have some more information, please, have a look at the user guide or this paper. The library is organized in 4 modules: vec: C++ classes relative to vector calculus (vector, rotation tensor, homogeneous transformation matrix, inertia tensor) + assignment methods and operators; sim: routines for integration of second-order differential equations; mbs: front-end to sim building the equations of motion from kinematics and applied efforts; visu: easy creation of files describing scenes composed of moving 3D objects for further visualization.