In-depth explanation of the “static” keyword in the C language.

The static keyword in C language has multiple uses, the meaning and purpose of each use will be explained below in detail.

1. Static variables in a function:
   Variables defined within a function are by default automatic variables, which can only be used within the function and are recreated and destroyed each time the function is called. However, variables declared with the static keyword are known as static variables, which do not get destroyed after the function call, but remain in memory. The static variable can still be accessed and used the next time the function is called. The initialization of static variables only occurs once during the program’s execution and is defaulted to 0.
2. Static functions within a function:
   Functions declared using the static keyword are called static functions, and they can only be used in the current file and cannot be accessed by other files. The purpose of static functions is to hide the implementation details of the function and prevent naming conflicts with functions in other files.
3. Static global variables within a file:
   Variables declared outside of functions using the static keyword are known as static global variables. They can only be used within the current file and cannot be accessed by other files. The purpose of static global variables is to limit their scope and prevent naming conflicts with global variables in other files.
4. Static functions within the document:
   Functions declared with the “static” keyword outside of functions are known as static functions. They can only be used within the current file and cannot be called by other files. The purpose of static functions is to hide the implementation details of the function, preventing naming conflicts with functions in other files.

In summary, the static keyword in C language has various uses, including defining static variables and functions within a function, as well as defining static global variables and functions within a file. The main purpose of the static keyword is to limit the scope of variables and functions, avoid naming conflicts with variables and functions in other files, and hide the implementation details of functions.