/*
H O W   T H E   C A L L   S T A C K   W O R K S
Ron Kessler
Created 1/1/2017

On windows the stack is 1MB in size and cannot be changed
*/


#include "stdafx.h"
#include <iostream>

using namespace std;

// function prototypes


int add (int x, int y);


//STEP 1: The main() method is pushed onto the stack by the O/S when we launch this app
int main ()
	{
	//the local variables on stored in the main() stack frame
	int result;


	//STEP 2: When this line runs the add function is pushed onto the stack in its
	//	own stack frame and all parameters/locals are stored with it. The add frame also holds
	//the memory location of the main() function so when add finishes, control can return ti main().

	result = add (50, 25);

	//STEP 4 With add() gone, main() is now on top of the stack so the app resumes executing until main finishes.
	cout << "The sum is: " << result << '\n';
	
	return 0;

	}

int add (int x, int y)
	{
	int answer = x + y;		//local var stored in the add() frame
	return x + y;					//return value can be held in the CPU registers or in the stack frame

	}	//STEP 3 Add is popped off the call stack here.