/*cbr.cpp 'Call-by-Reference' program.
*This program illustrates the role of call by reference and
* the scope of variables.
*/

#include<iostream>

using namespace std; 

/* Next, we have a call-by-reference formal parameters
* are holding spaces for the actual arguments in a function call.
* A formal parameter is made a call by reference parameter by appending the
* '&' after its typename and the vartiable that follows should be a non-constant.
* Upon a call for get_numbers, the corresponding variable argument and not its value will be substituted
* for the formal parameter.
* Any change made to the formal parameter will be made to the argument varaible when the function is called. 
*/
void get_numbers(int& input1, int& input2)
{

cout<< "Enter the two integers: "<<endl;
cin >> input1 
    >> input2 ;
/*When instructions in the body of this function are executed, 
* the changes to the function body are implemented for example
* at memory 101a, value stored is now input1.
*/
}
void swap_values(int& variable1, int& variable2)
{

int temp ;
temp = variable1;
variable1= variable2 ;
variable2 = temp;

}
void show_results(int output1, int output2)
{

cout<< "In reverse order the numbers are: "
    <<output1 << " " << output2 <<endl; 
}


int main()
{

int first_num(2), second_num(0); 
/* We begin by values 2 and 0 held at memory locations &first_number
* and &second_number respectively let us enumerate these memory addresses by 101a and 102b say.
*/
get_numbers(first_num, second_num);
/* When the function call is executed, the function is not given the values stored at 
* first place and second place. Instead, the compiler reads the memory locations namely
* 101a and 102b.
*When the function get_numbers exits, variables input1, input2 go out of the scope and
* are lost. This means we can no longer retrieve the data values at 101a & 101b.
* However, the data exists at these memory locations and can instead be accessed by first_num and
second_num.
*/
swap_values(first_num, second_num);
show_results(first_num, second_num);
return 0;
}