Growth in Knowledge of Programming Patterns: A Comparison Study of CS1 vs. CS2 Students

How does students' knowledge of code structure improve as they progress through their degree, and where do students struggle? We conducted a comparative study between introductory (CS1) and intermediate CS students (CS2) to explore these questions. Using an online survey with several tasks, including identification of expert patterns, judgment of readable structure, code comprehension, code writing, and editing, we focused on two important code structures: (S1) returning boolean expressions directly and (S2) unique vs. repeated code within if and else. Student performance varied based on structure and task: in both S1 and S2, CS2 students demonstrated higher performance in identifying patterns, judgment of readable structure, and editing. However, evidence of improvement in code writing was only found for S1, and improvement in code comprehension was only found for S2. Therefore, students may need different supports across different code structures. With the exception of comprehension of S1, student performance was far below ceiling, suggesting a need for more support.