A direct manipulation language for explaining algorithms

Instructors typically explain algorithms in computer science by tracing their behavior, often on blackboards, sometimes with algorithm visualizations. Using blackboards can be tedious because they do not facilitate manipulation of the drawing, while visualizations often operate at the wrong level of abstraction or must be laboriously hand-coded for each algorithm. In response, we present a direct manipulation (DM) language for explaining algorithms by manipulating visualized data structures. The language maps DM gestures onto primitive program behaviors that occur in commonly taught algorithms. We performed an initial evaluation of the DM language on teaching assistants of an undergraduate algorithms class, who found the language easier to use and more helpful for explaining algorithms than a standard drawing application (GIMP).