[coldtea]

>Whenever I try to understand a program, I do draw structures of it. But it is NEVER the structure of the source code as is, but some parts the main flow with the unimportant bits left out

While some tools might be more or less accommodating, there's nothing about visual representation per se that can't do that (including filtering the non-important parts, producing something akin to UML's interaction diagrams, etc).