During one of my internships, a company I worked with encapsulated their C code. To me, it felt familiar to the Object-oriented programming I was used to (C++ and Java).

“Object-oriented C??”, I gasped. I never heard of such a thing.

I knew that you could use the static keyword in C to encapsulate variables to the scope of the file as so:

static int _hidden_value = 0;

void public_function()
{
	// read or modify _hidden_value
}

And I knew you could use static to encapsulate functions to the scope of the file as well:

static void private_function_1(void);
static void private_function_2(void);

void public_function(void)
{
	private_function_1();
	private_function_2();
	return;	
}

Using static as so for variables and functions will already will make your C code cleaner. This is essentially having private functions and variables, except in C! If you need to access the private variables, you can even create getter and setter functions.

In this way, a C-file becomes a janky C object with its own set of private functions and public APIs. For medium to large C projects, using static really shines by keeping code organized and tidy!