Control flow graphs are well-known in computer science and especially in software engineering and used for a variety of applications. They describe functions or programs with respect to their control flow as directed graphs. Unfortunately, there are many different definitions of control flow graphs on different detail levels. In this paper we give a uniform definition of control flow graphs that subsumes several other definitions. The approach is based on the notion of graph reductions. This allows us to clarify different definitions of control flow graphs found in the related literature and, furthermore, to present an approach to find other useful control flow graph representations of programs. Another application of this approach is the step-by-step reduction of control flow graphs in the analysis of programs, for example, in the design of test cases in software engineering.

control flow graph, graph reduction, decision graph, source code analysis.