(If you think another site on StackExchange or elsewhere is a better location to ask this type of question, please point me in the right direction.)
What do experienced developers use to figure out how the code of an existing application work, before being able to modify/add to it?
Is there a more productive way than going through line by line with pen/paper handy until you figure it out? I find it time-consuming, and difficult to keep the big picture and not get lost with details.
For instance, is there some application that would parse source code and somehow draw a diagram showing the logic in some kind of zoomable storyboard?
Thank you.