Computer technology is allowing previously expensive functions to now be available at low cost - from engineering applications to machine tool programs. This reduction in cost is allowing the computing functions to be distributed (e.g., CNC), which if left alone would be regrettable, since previously centralized, coordinated functions would now be independent, autonomous, redundant, etc. Hence the role of the Local Area Network (LAN) - to recover the loss that would otherwise occur if computing were continuously subdivided into smaller and smaller, more distributed parts.LANs have evolved during the past ten years to the point where they are now in popular use in many applications. The lack of a single LAN standard, however, has stimulated the development of heterogeneous networks - those comprised of combinations of dissimilar LANs. Heterogeneous LANs and their applications is the subject of this paper.