Computer simulations are increasingly used to study the development, adoption, and evolution of technologies. However, existing models suffer from various drawbacks that may not be easily corrected, among them lack of internal structure in technologies, static environments and practical difficulties of introducing rational or semi-rational search for solutions. This paper discusses the theoretical background and rationale for an improved model, the Adder, and sketches out the model's main features. © ECMS Klaus G. Troitzsch, Michael Möhring, Ulf Lotzmann (Editors).