Sorting things into groups is a basic intellectual task that allows people to simplify with minimal reduction in information. Classification techniques, which include both clustering and discrimination, provide step-by-step computer-based procedures for sorting things based on notions of generalized similarity and on the "class description" desired. This paper surveys and classifies all classification techniques known to the author. A conceptual framework for considering these techniques is developed. Useful techniques for interpreting and evaluating the results are given. An extensive bibliography is included. (Author)