Program comprehension with four-layered mental model

Program comprehension deals with an important problem of recreating mental model of the software system from the source code. This process is needed every time a new programmer joins the development team, or the old one forgets about the code. We designed the four-layered model of the developer's mental model that provides a deeper understanding of the mental model and of the program comprehension in general. The described model was verified by an observatory study with 3 subjects. This paper concludes with our findings and conclusions.