How to import external files in C language?

In the C language, external files can be imported using the #include directive. This can include standard library files as well as custom header files.

For example, to import the standard library file stdio.h, you can use the following code:

#include <stdio.h>

To import a custom header file, such as myheader.h, you can use the following code:

#include "myheader.h"

After importing the header file, we can then use the functions, variables, and other contents defined in the header file.