EVALUATING PROGRAM REPRESENTATION IN A DEMONSTRATIONAL VISUAL SHELL Francesmary Modugno Albert T. Corbett Brad A. Myers Carnegie Mellon University Pittsburgh, PA 15213 ABSTRACT For Programming by Demonstration (PBD) systems to reach their full potential, some way of representing programs is necessary so that programs can be viewed, edited and shared. How to represent programs, especially in a way that is easy for non-programmers to understand, is an open question. We designed and implemented two representation languages for a PBD desktop similar to the Apple Macintosh Finder. The first language is based on the comic-strip metaphor and graphically depicts the {\it effects} of a program on data. The second language is text-based and describes the {\it actions} of a program. A user study revealed that both languages enabled non-programmers generate and comprehend programs containing loops, variables and conditionals. Moreover, the study revealed that the comic-strip language doubled users' abilities to accurately generate programs. Trends suggest that the same language was also easier for users to comprehend. These findings suggest that it is possible for a PBD system to enable non-programmers to construct programs and that the form of the representation can impact the PBD system's effectiveness.