Code comments improve software maintainability, programming productivity, and software reliability. To address the comment scarcity issue in many projects and save developers’ time in writing comments, we propose a new, general automatic comment generation approach, which mines comments from a large programming Question and Answer (Q&A) site. Q&A sites allow programmers to post questions and receive solutions, which contain code segments together with their descriptions, referred to as code-description mappings. We develop AutoComment to extract such mappings, and leverage them to generate description comments automatically for similar code segments matched in open source projects. We apply AutoComment to analyze 92,140 Java and Android tagged Q&A posts to extract 132,767 code-description mappings, which help AutoComment generate 102 comments automatically for 23 Java and Android projects. The number of generated comments is still low, but the user study results show that the majority of the participants consider the generated comments accurate, adequate, concise, and useful in helping them understand the code. One of the advantages from mining Q&A sites for automatic comment generation is that human written comments can provide information that is not explicitly in the code. In the future, we would like to focus on improving both the yield and quality of the generated comments. To improve the yield, we can replace the token-based clone detection tool with one that can detect addition and reordering of lines to increase the number of code matches. To improve the quality, we can apply advanced natural language processing techniques such as semantic role labeling to analyze the semantics of the sentences, or typed dependencies to analyze the grammatical structure of the sentences.

This thesis describes the implementation of a Controlled English Commenting (CEC) system that aids a VHDL modeler in entering controlled English comments. The CEC system developed includes a graphical user interface (GUI). The interface permits a modeler to submit comments for insertion at user selected points in a text file containing the model. A submitted comment is analyzed for vocabulary and syntax, and is then inserted if it is controlled English. If it is not, the CEC system extracts all possible controlled English comments that can be formed from the original comment and presents them to the user for selection and entry into the model. The interface then queries the user to complete any residual portions of the original comment until the user is satisfied. Until the user becomes familiar with the constraints of the controlled language, significant interaction is needed, particularly on complex comments. Preliminary experiments indicate that users rapidly learn the language's constraints and the need for interactive help declines. / Master of Science