Method for keeping records in a computer science notebook?
Based on what you say about yourself, I'd guess that the Cornel system is probably better than either of the other two described here. But that is just because you suggest that you seem to lack the ability, currently, to pull out the big ideas as they occur and the other two methods depend on doing that. 

But, the goal of all of this isn't really effective note taking. You can have the best notes in the world and still not learn anything. The goal is to learn and to do that you need to reinforce the ideas that are presented, not just capture them in notes. But note that the Cornel system, as described at the link, includes this step as an essential part. Review the notes you take. 

I'd go farther, actually. Not only review the notes, but write summaries of them periodically. And don't wait too long before doing that, so you don't lose the track of what you were learning in the meantime. 

Another reinforcement trick is to write the important ideas on note cards and always carry a few of these around with you, along with a few blank cards and a pen. Then you can review while otherwise spending wasted time waiting for a bus or whatever. 

But in a subject like CS or mathematics where you are actually expected to do something with what  you learn, it is also important to do exercises and solve problems soon after any lesson. This will, again, firm up the learning. Even better if there is someone to give you feedback on your solutions. This normally happens when exercises are assigned, but you might have to arrange it on your own for others. Study groups can be useful for this if they are well designed, requiring actual work from every member. Reading solutions is nothing like producing them. 



For what it's worth I now just capture ideas on directly on note cards. One idea per card. I can then group and rearrange the ideas by physically manipulating the cards. Summaries can be developed from the cards. Questions can be written on the backs of the cards. Different colored cards can be used for different sorts of things.