| With the growing use of PDAs and the growing number of end-user programmers it seems natural to create an end-user programming language for the PDA, where applications can be programmed on a PDA and run on a PDA.; PdaGraph, an end-user, component-based programming language for the PDA, is a programming language in progress. In the first stage a data-flow visual programming language was designed. It was quickly observed that by itself, the data-flow language is lacking an intuitive user interface and the connections between different parts of the program are not visible.; To overcome this problem we designed a high-level component-based message-flow programming language and environment that will make PdaGraph suitable for end-users. To verify that the design is end-user friendly we conducted a usability study using a low fidelity paper prototype.; The usability study included one cycle of four usability tests, followed by analysis of the results and changes to the prototype stage, and a second round of four usability tests to verify the modified prototype. During the study, feedback was obtained by videotaping the subject-system interactions and using a cognitive dimensions questionnaire.; In this work we introduce the message-flow programming language architecture and design. We describe the usability study, the feedback that we received from the subjects, and the changes that we put into the design as a result. |
