Events-first programming in APP inventor

Events are a central concept in computer science. They are becoming more important with the prevalence of mobile and web platforms that use event-based programming. Yet, events are typically taught late in the CS curriculum -- e.g., in a web programming or operating systems course. We have introduced events to CS0 students from day one using MIT App Inventor, a blocks-based programming environment that enables students to create apps for Android devices. This paper presents the system's event-based model, along with typical coding problems and best-practice approaches for solving them. We advocate for increasing early emphasis on events in the CS curriculum.