We present here a computational, macroeconomic model with decentralized markets. The modeled economy is always out of equilibrium. It is composed of two principal sets of agents (firms and households) associated with two main functions (production and consumption). These agents operate within the framework of a capitalist economy (private means of production, monetary exchange, wage earning). The agents are autonomous individuals who are placed in direct and indirect interaction with each other (and not mere representative agents or aggregates). Each agent pursues his own purposes, acts according to his individual context and his local environment; he is unconcerned about the general equilibrium of the system and he is not subject to over-riding control (neither from a planner, nor from an auctioneer). The model implements the three main characteristics of monetary economies: - Production takes time and firms need credit to launch the production process; - Money is endogenous, created by bank credit that is issued for the purpose of production; - Firms are led by a profit motive and profits are realized in terms of money. Java-based, the model provides a virtual laboratory that makes it possible to run experiments "in silico". Real and monetary interactions between agents (which are multiple, heterogeneous, autonomous and rival) form a dynamic, complex system, the properties of which we do not postulate. Thus, the model reconstructs the conditions of the emergence of macroeconomic patterns, which cannot be observed in models that are based on notions of a representative agent and general equilibrium.
