(preface:? In fact, there are many articles on this topic on the Internet. Why is there this article? There are so many reasons, which are the driving force of my translation. First, although the concept and content are old-fashioned, they are very thorough and comprehensive Second, theory is combined with practice, and the case analysis is good Third, it is not fancy. The tools and commands used are the most basic and helpful for practical operation However, this person is not very knowledgeable. Most of the translations are based on his own understanding of the original text. You can also go to oscan by yourself? If there is any major discrepancy, please leave a message and reply. Thank you very much!)