How can I teach myself the course of computer principles if I want to upgrade to a junior college?

  c++, question

There should be a lot of users who come from cs courses on this website. How did you learn this course at the undergraduate level? The title owner wanted to upgrade from a junior college to a junior college, bought a book and planned to study on his own. However, he felt that there was no teacher to teach him, and it was a bit difficult to read alone. It seemed that some knowledge such as model electricity, digital electricity and so on were involved in it. My current specialized scientific software is completely web development, and I have not come into contact with these. At the end of the semester, I plan to collect the notes of local undergraduate college graduates. Is there any other good learning route or proposal besides this? Hope to get your valuable advice, thank you.