Block-based or graph-based? Why not both? Designing a hybrid programming environment for end-users

Abstract End-user programmers need programming tools that are easy to learn and use. Development environments for end-users often support one of two visual modalities: block-based programming or data-flow programming. In this work, we discuss differences in how these modalities represent programs, and why existing block-based programming tools are better suited for imperative tasks while data-flow programming better supports nested expressions. We focus on robot programming as an end-user scenario that requires both imperative and expressions-based code in the same program. To study how end-user tools can better support this scenario, we propose two programming system designs: one that changes how blocks represent nested expressions, and one that combines block-based and data-flow programming in the same hybrid environment. We compared these designs in a controlled experiment with 113 end-user participants who solved programming and program comprehension tasks using one of the two environments. Both groups indicated a small preference for the hybrid system in direct comparison, but participants who used blocks to solve tasks performed better on average than hybrid system users and gave higher usability ratings. These findings suggest that despite the appeal of data-flow programming, a well-adapted block-based programming interface can lead end-users to more programming success.