Last year, while preparing for a career change as a developer, I learned about Younghan's lectures, and I have taken all of them since then. I have never thought that any lecture was a waste of time or money. In particular, I started with the basic concepts, which is Younghan's teaching style, and naturally solved my curiosity about why it is necessary, and further, I was able to learn how it is used from a practical perspective, so I understood everything that was taught in each lecture. I still have a long way to go, but I am growing step by step by listening to Younghan's lectures. I am so grateful to Younghan for recording the lectures! And I hope there will be a lecture on databases sometime. ><