Exploring Graphical Feedback in a Demonstrational Visual Shell (Abstract) Francesmary Modugno and Brad A. Myers School of Computer Science Carnegie Mellon University Pittsburgh, PA 15213 USA We present a visual language that serves as a novel form of feedback in a Programming by Demonstration (PBD) interface. The language explicitly represents data, such as files, with unique icons and implicitly represents operations by changes to data icons, so that operations reflect the changes seen in the interface when executed. In addition, the language is used to provide feedback to the user by indicating loops and inferred sets, specifying parameters, etc., and is integrated into other parts of the PBD system, such as the editor. This forms a close union between the interface, the PBD system and the program representation and helps bridge the gap between the user's mental model of the programming process and the actual programming task.