Modules in C are called functions. C programs are typically written by combining user-created functions and "pre-packaged" functions found in the C Standard Library. For instance, printf() is a function that is found in the C Standard Library and is accessed through the stdio.h header file.

you are going to focus on creating your own functions. You can create a function that can do any kind of task. For instance, the function may display a message to the screen or compute a value.