A microcomputer based software package for the graphic simulation of fundamental binary search tree algorithms is presented. This application was developed to augment instructional aids available to the instructor during classroom lecture. The system is mouse controlled and was designed to be used on an IBM PC compatible microcomputer connected to either a large screen video monitor or a projection display. Several screen dumps are presented to illustrate the multi-level graphical representation of trees, pseudocode algorithms, and window environment incorporated in the package. In addition, the literature on CAI oriented simulations for Computer Science topics, with a focus on data structures, is reviewed briefly. Computer Aided Instruction (CAI) is an educational application area with tremendous potential. The recent advent of reasonably priced personal computers with medium resolution color graphic capabilities will hopefully increase the generation of CAI materials in all fields. Ironically, there has been little CAI material developed to aid in the instruction of Computer Science. Furthermore, earlier efforts at courseware development for computer science was centered on programming languages not more advanced topics. In recent years, however, several researchers have been developing personal computer based courseware simulations of more advanced topics: program execution [2,6,21,16], computer architecture [15,17], and data structures algorithms. This work is part of a growing body of research being performed in the emerging area of Visual Programming [11,10]. In this paper we will first briefly review the area of graphic simulations of fundamental data structures and their algorithms. Second, we will describe the CABTO (Computer Animation of Binary Tree Operations) package. We developed CABTO to be used as a lecture aid in a lower division data structures course.