This paper focusses on the challenge of building and programming scalable concurrent computers. The paper describes the inadequacy of current models of computing for programming massively parallel computers and discusses three universal models of concurrent computing — developed respectively by programming, architecture and algorithm perspectives. These models provide a powerful representation for parallel computing and are shown to be quite close. Issues in building systems architectures which efficiently represent and utilize parallel hardware resources are then discussed. Finally, we argue that by using a flexible universal programming model, an environment supporting heterogeneous programming languages can be developed.