This paper describes a highly interactive computer program, ABACUS, which exploits the potential of microcomputers in a mathematical sciences laboratory. In contrast to most educational software which demonstrates very specific points, ABACUS can be used for a variety of applications: it allows one to plot one or more functions on the same set of axes, to differentiate analytically, to compute a definite integral, to search the zeros of a function, and to solve systems of differential equations and to generate Taylor series expansions.