It might be useful to document some important functions, processes or features in a semi-formal notation.
Consider the open-source PlantUML (http://plantuml.com/) as an example. Given the following activity description, it can create a graphical version:
@startuml start :authenticate; :select product; if (private customer?) then (yes) :add\nVAT; else (no) :request\nVAT_ID; endif :create invoice; stop @enduml
Activities are described between: and;, branches can be read as pseudo code and that way you combine the benefits of plain text with graphical representation.
PlantUML renders the code above to the following diagram: