The second role: Modify the function. Adding static before the function makes the function a static function. But here's the meaning of "static"
Not referring to storage, but rather to the scope of the function is limited to this document (so it is also called an internal function). Use internal letter
The advantage of the number is: When different people write different functions, do not worry about the function you define, whether it will be with other files
The function in the same name.
The keyword static has an unusual history. Initially, the keyword static was introduced in C to signify exiting
Local variables that still exist after the block. Later, static has a second meaning in C: used to indicate that it cannot be used by other files
Access to global variables and functions. To avoid introducing new keywords, we still use the static keyword to represent this second
Kind of meaning.