On the knowledge required to understand a program

This paper is concerned with the units of knowledge used in understanding programs. A pilot study was conducted wherein a short, but complex, program was examined looking for knowledge atoms, the units from which program understanding is built. The resulting atoms were categorized along three orthogonal axes of knowledge type, design decision used, and the type of analysis required to uncover the atom. The results are discussed relative to several approaches to program understanding taken from the research literature