The number of industrial robots used worldwide has been continuously increasing. In almost all cases the application program has the form of a text based source code, which has inherent drawbacks (in terms of complexity and ease of development) when compared to the graphical approaches seen in general purpose software engineering. These graphical programming approaches have not been developed, having industrial robots in mind. In this paper a behavior trees based approach for creating and representing source code for robotic applications is proposed. The software architecture and an experimental implementation of the developed programming method is presented and a validation using a common assembly task is shown.