How to read large sources, analyze large systems?

Question

Programming

When I open large listings in the middle, I already forget what happened at the beginning.
What I think about the question:
1) It is necessary to break large systems into subsystems, to highlight patterns.
2) Build UML diagrams on the source code or somehow visualize the code.
3) Use special software, such as SourceInside
What approaches do you use? (yes, I understand that experience is needed, but what if there is not enough experience yet?)
UPD: I'm not asking how cool you are and how cleverly you use Notepad. I'm asking about how to think (how you think) when analyzing sources.

Answer 1

Try running a Sparx Enterprise Architect project. Lightweight and highly functional. It will show you the project structure and connections, and then it will be easier.
It is paid, but there is a trial version - it will be quite enough for analysis.

Answer 2

I start with this:

Answer 3

Probably, a good architectural abstraction of the project helps here. Large listings become small, or at least break down into logical entities. While the project is being built, just stubs are written, then these stubs are implemented.
But in any case, the most important, global architecture should be thought out in advance, so that later you don’t have to keep the whole project in mind =) in the brain must be placed with the necessary accuracy.

Answer 4

A large system cannot be studied quickly, you read it once, the second, the third, on the tenth you no longer forget what happened at the beginning.

Answer 5

The IDE helps a lot, I used to use eclipse, now I discovered NetBeans and I like it better. There is navigation through the code (the methods of the source code are described in order). I often use this functionality - as a cheat sheet. And of course, good comments in the code really help to clean up the head.

Answer 6

You won’t believe such people, but the most convenient way for me personally is Sublime Text 2 (3) with its enchanting Cmd + P (quickly rummage through the project), Cmd + R (quickly rummage through the code) and Cmd + T (quickly rummage through tabs).
But in general, yes, to highlight patterns, build diagrams, collect meetings and generally behave appropriately.