In school exams, you can not read textbooks during the exam. In other words, you can not input when output. However, programming is different. While writing a program, for example, if you can not recall the command to combine strings, You can input information immediately by reading the textbook or searching on the Internet. Then you use the input information right away to write the program.
In other words, each line of programming is a small test. You can input what you could not recall immediately. After inputting, you immediately output the program using the knowledge. You try to output, input what you can not output, and output it again. You can turn the learning cycle very fast.