Many of us write code regularly as part of our scientific activity, perhaps even as a full-time job. But even though we write--and use--more and more code, we rarely think about the roles that this code will have in our research, in our publications, and ultimately in the scientific record. In this article, the author outlines some frequent roles of code in computational science. These roles aren't exclusive; in fact, it's common for a piece of code to have several roles, at the same time or as an evolution over time. Thinking about these roles, ideally before starting to write the code, is a good habit to develop.