Source code reuse evaluation by using real/potential copy and paste Developers often reuse existing software by copy and paste. Source code reuse improves productivity and software quality. On the other hand, source code reuse requires several professional skills to developers. In source code reuse, developers must locate reusable code fragments, and judge whether such reusable code is adequate to copy and paste into the source file under development. This paper presents extraction and analysis methods for developers’ source code reuse behavior (copy and paste). Our method extracts developers’ actual source code reuse (real copy and paste). Then, by using a code clone detection tool, the method extracts code fragments for (potential reuse). Our study of real and potential copy and paste provides a quantitative assessment for source code reuse by developers.