When programming, students often stumble across typical syntax errors such as forgetting the semicolon at the end of a command, the curly bracket at the end of a block, or run-time errors such as null reference exceptions. The compilation errors are often difficult to understand, or the error misleadingly points to the next (e.g., forgotten semicolon) or last line (e.g., forgotten closing brackets). This thesis aims to determine typical learner errors using a series of tasks and write an extension for an online Kotlin programming environment, supporting the students in finding and correcting errors independently. Based on the typical errors from literature and the errors found in the material-testing group, the standard compilation error messages are supplemented by user-oriented error messages. Those consist of up to a user-oriented prob-lem formulation, a solution hint, a typical example, a link to the relevant point in the manual, and an exact location display. The effect of the error extension is determined with the control group design based on quantitative (solution time, number of attempts until solved) and quali-tative measured values (feedback questionnaire) in comparison between the test and control group.
