Types, Distribution, and Test and Correction Times for Programming Errors

This paper reports the results of an experiment whose objectives were to: 1. Develop and utilize a set of terms for describing possible types of errors, their nature, and their frequency; 2. Perform a pilot study to determine if data of the type reported in this paper could be collected; 3. Investigate the error density and its correspondence to predictions from previous data reported; and 4. Develop data on how resources are expended in debugging. A program of approximately 4k machine instructions was chosen. Programmers were asked to fill out for each error, in addition to the regular Trouble Report (TR)/Correction Report (CR) form, a special Supplementary TR/CR form for the purposes of this experiment. Both the regular and the Supplementary forms were divided into two sections. Each form consisted of a single sheet; the upper half of each form was the Trouble Report (TR), and the lower half of each form was the Correction Report (CR). Sixty-three regular and Supplementary TR/CR forms were completed during the Test and Integration phase of the program; these forms represented a little over 1.5% of the total number of machine instructions of the program (in good agreement with the 1% to 2% range noted in previous studies). A large fraction of the errors was found by hand processing (without the aid of a computer), which was much cheaper than machine testing.