AbstractModuleco is a time-sharing system specialized on simulation and optimization of large macro-economic models (1 000 equations). These models are deterministic, non linear and written asft(xt,xt−1,....,xt−p)=0.​​​​​​​ΑMODULECO user disposes of a new modelling language. The software translates the equations into an internal code which is used by the simulation and optimization algorithms.We hereby present the simulation results obtained on these kinds of models and an example of simulation using the MODULECO language.Simulation methods adapted to the particularities of an economic model matrix have been used. These methods were developed by the MODULECO team. Experience with them has shown that we obtain better matrix decomposition and resolution times.The Moduleco language provides a set of basic commands and an extension mechanism. The user has the possibility of combining existing commands under the control of a program. Such a program may later be defined as a new command in Moduleco. Such a program as well as the command language are interpreted. A new command may also be defined by giving reference to a program written in a programming language.The calling of such a command at the terminal will result in the execution of the associated program.