We examine students' commonsense understanding of computer science concepts before they receive any formal instruction in the field. For this study, we asked students on the first day of a CS1 class to describe in English how they would arrange a set of numbers in ascending, sorted order; we then repeated the experiment asking students to sort a list of dates (in mm/dd/yyyy format). We found that a majority of students described a coherent algorithm; some described versions of insertion or selection sort, but many gave unexpected algorithms. We also found significant differences between responses given for sorting numbers versus dates. Based on our analysis of the data we suggest that beginning-programming instructors more explicitly discuss data types, begin loop instruction with post-test loops, assist students in recognizing implicit conditional and iteration use in natural language solutions to problems, and recognize that novices and experts focus on different aspects of the problem in even basic problem solving tasks.
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