Jiig

I've been tasked to try and learn how some very old C++ code base (30k plus lines) at my job, I've heard that its originally from the late 90s and has been updated periodically, since it preforms some very crucial processing.

The code is commented fairly well but is missing any sort of top-level architecture documentation or explanation.

I've started by just following the flow, but am getting very very lost. Are there any tips you have to help me wrap my head around this?