An investigation of the on-line debugging process of expert and novice student programmers

Graduation date: 1988Debugging, the process of locating and correcting errors in a computer\ud program, is a common programming task that is not well understood. Of the\ud several debugging studies reported in the literature, most compared the performance\ud differences between expert and novice programmers by measuring\ud their debug time and the number of errors found and corrected; a few provided\ud information about their debugging process. This dissertation investigates\ud the on-line debugging process of expert and novice student programmers\ud by means of protocol analysis.\ud This dissertation describes three debugging experimentations that were\ud conducted to understand the debugging process and were used as the basis for\ud a cognitive model of subjects' on-line debugging behavior. In the three experiments\ud subjects debugged a defective Pascal program seeded with several errors\ud on a Apple Macintosh computer.\ud Some of the major results obtained through this research work are summarized\ud below:\ud Experts employed a comprehension approach in which they first\ud attempted to understand the program and then used this knowledge for\ud finding the bugs. Intermediates and novices employed an isolation\ud approach in which they immediately attempted to identify candidate bug\ud locations by searching the output for clues, recalling similar bugs, and\ud testing program states.\ud Experts corrected multiple errors before verifying the corrections while\ud novices corrected and verified single errors. Novices corrected the semantic\ud errors first and then the logic errors while experts corrected both\ud semantic and logic errors at the same time.\ud Experts were more efficient in correcting all of the errors, modified fewer\ud statements, and did not introduce more errors. Novices did not correct\ud all of the errors, made very extensive modifications and introduced many\ud new errors.\ud Program understanding played a key role in locating and correcting logic\ud errors.\ud Experts' superiority in locating and correcting errors was due to their\ud better (a) overall understanding of the program, (b) ability to identify\ud program segment containing the error, and (c) ability to select a correct\ud error hypothesis