Abstract
This work proposes a simple model to simulate the dynamics of the market related to COTS software products, when there are no new entrants. The model takes in explicit account the interactions between products. The model uses a set of random variables, as the initial condition, to simulate the time evolution. The results of the simulations predict the emergence of monopolies, when the interactions between products are significant, and of open markets, when they are limited. The model is validated, by comparing the results of the simulation with the well established observations related to software markets and by comparing the resulting distribution of COTS software products with real data on the software market, which was provided by PC Data Inc.