Recent years have seen considerable progress in computer technology, in computer science, and in the computational sciences, which include computational chemistry. To a large extent developments in these fields have been mutually dependent. Progress in computer technology — such as the use of very-large-scale integrated circuits — has led to increasingly larger and faster computing machines, the so-called supercomputers, as well as powerful minicomputers. At the same time, research in computer science has explored new methods for the optimal use of these resources, such as the formulation of new algorithms that allow for the maximum amount of parallel computation. Developments in computer technology and computer science have had a very significant effect on the computational sciences and in particular on computational chemistry.