This book is based on the book "C Programming Fifth Edition" written by Tan Haoqiang, contains the answer to each chapter of the topic, each topic is I first use the VS2019 compiler to knock once, and then write the code ideas to CSDN, and then posted to the column. When encountering a topic that I do not know, I will go online to search for relevant code and solution ideas, understand and then practice on the machine until the result is correct. This exercise is divided into three parts: A solution, B code, C running results. As long as there is code for each problem, there will be results to verify, so the correctness of this exercise analysis is trustworthy. There is a joke in programming "Treat computers like girlfriends, because computers are never wrong." If a program fails to run, it must be our problem, that is, our code has more or less grammatical errors and logical errors. For beginners, program errors are normal, I recommend that we use VS2019 compiler for more practice, in the program error must be more debugging, so that we can feel how the program runs, and the process of running the program.