如果把两个函数的位置对换一下,即先写main函数,后写max函数,这时在编译main函数遇到max时,编译系统无法知道max代表什么含义,因而无法编译,按出错处理｡

-If the position of the two functions change, the first to write the main function, written after the max function, At this time, the compiled main function encounters max, the build system can not know max What is the meaning, and thus can not be compiled by the error handling.