program to understand actual parameter and formal parameter

• Formal and actual parameter are associated with the concept of 'call by value' and 'call by reference'
• see the effect of 'call by value' and 'call by reference'

====================================================
//this program to illustrate call_by_reference
#include <iostream>
using namespace std;

int add(int &);

int main()
{
    int a=2;
    int square;
    square = add(a);
    cout << "\n" << a;
    cout << "\n" << square;
}

int add(int &a)
{
    a=a+1;
    return(a*a);
}

OUTPUT:
3
9


====================================================== 
// this program to illustrate call_by_value
#include <iostream>
using namespace std;

int add(int);

int main()
{
    int a=2;
    int square;
    square = add(a);
    cout << "\n" << a;
    cout << "\n" << square;
}

int add(int a)
{
    a=a+1;
    return(a*a);
}

OUTPUT:
2
9 

======================================================
// This is a extra program to understand 'actual' and 'formal' parameter
// which associated with the 'call by value' and 'call by reference'
#include <iostream>
using namespace std;

void add(int a, int b)      //here a, b are formal parameter
{
    int c = 0;
    c = a + b;
   
    cout << "\n Addition of 2 number is: " << c << endl;
}

int main()
{
    int a=0;
    int b=0;
    int c=0;
    int d=0;
   
    cout << "\n Please Enter 2 number: ";
    cin >> a >> b;
   
    d = a-b+c;          //actual parameter
    cout << " \n substraction is(d): " << d << endl;
   
    add(a, b);     //actual parameter
}