This isn't a programming related question but Structure Charts are probably your best bet.
http://en.wikipedia.org/wiki/Structure_chart
This may also be of interest:
Question
Currently I'm writing a theses for software project, Which uses structural programming techniques. DFD,Context diagrams may helps to depict the software, is there any other diagrams could help to describe the software?
Solution
This isn't a programming related question but Structure Charts are probably your best bet.
http://en.wikipedia.org/wiki/Structure_chart
This may also be of interest: