Swan is a data structure visualization system. Using Swan, a C or C++ program can be annotated to provide multiple views of the data structures used in the program so that they can be better understood by the viewer. Swan allows visualization to be a two-way communication process between the viewer and the program. Several automatic graph layout algorithms are implemented in Swan for layout of various data structures. Automatic layout allows the annotator to concentrate on the logical views of data structures without worrying about their graphical display. Swan serves as a data structure visualization system, a graphical debugging tool, and a platform for experimenting with graph layout algorithms. / Master of Science