How to use return function in recursion.

void inOrder(struct node* r)
{
printf("inoder %d ",(int) r);//debug output
if (r==NULL)
return;
 else{
//do your recursion work
printf("l-call: %d ", l->value);
inOrder(r->left);
printf("r-call: %d ", r->value);
inOrder(r->right);
    }
}

void main()
{
	struct node *pn;
	int a = 5, b = 8, c;
	
	...
	<some code>
	...
	inorder(pn);
	c = a + b;     // address of this instruction is 12345680
	<some more code>
}

int fun()
{
	struct node n;
	
	...
	<some code>
	....
	
	inorder(&n);
	getchar();   // address of this instruction is 12345760
	<some more code>
}

void inorder(struct node *r)
{
	if (r==NULL)
		return;
	else
	{
		inOrder(r->left);
		printf("%d ", r->value);  // address of this instruction is 12345900
		inOrder(r->right);
	}
}

/*
	JUST before calling inorder()
	in the call from main() the value 12345680 is pushed onto the stack
	in the call from fun()  the value 12345760 is pushed onto the stack
	in the (recursive) call from inorder()  the value 12345900 is pushed onto the stack
	
	i.e. in each case the address of the next instruction (immediately following the function call) is pushed onto the stack
	so that processing continues from this point (next instruction) in the CALLER after the called function completes normally 
		(end of function OR  'return' instruction in the middle of the function)
	It makes no difference whether the call is recursive or not.
	if you have some idea of 32 bit x86 registers 
		'eip' always holds the address of the instruction to be executed next
		'esp' points to the last value pushed on the stack - 
			this is the return address (12345680 / 12345760 / 12345900) in our example
		the 'return' instruction will result in something like this (in C syntax):
			eip = *esp++; // esp++ since stack grows downward (generally including x86)
			
			Since 'esp' points to these values, the return address is automatically assigned to 'eip'
		So processing continues from whatever instruction 'eip' points to i.e. next instruction in CALLER.

*/

Quote:

I am having this silly doubt