Call by value - C
  
 Source Code
  

    
#include<stdio.h>
 
void Swap(int a, int b);

void main() {
  int a, b;
  printf("Enter the value of a:  ");
  scanf("%d",&a);
  printf("Enter the value of b:  ");
  scanf("%d",&b);
  system("cls");

  printf("Before calling Swap() :  a = %d   &   b = %d",a,b);
  Swap(a,b);
  printf("\n\nBut not Swapped inside main() :  a = %d   &   b = %d",a,b);
}

void Swap(int a, int b) {
int temp = a;
       a = b;
       b = temp;
    printf("\nSwapped Inside Swap() :  a = %d   &   b = %d",a,b);
}
    

Enter the value of a:  5
Enter the value of b:  9

Before calling Swap()     :  a = 5   &   b = 9
Swapped Inside Swap() :  a = 9   &   b = 5

But not Swapped inside main() :  a = 5   &   b = 9

  
Call by reference - C
 Source Code

  
#include<stdio.h>
    
void Swap(int *a, int *b);

void main() {
  int a, b;
  printf("Enter the value of a:  ");
  scanf("%d",&a);
  printf("Enter the value of b:  ");
  scanf("%d",&b);
  system("cls");

  printf("Before Swapping:  a = %d   &   b = %d",a,b);
  Swap(&a,&b);
  printf("\nAfter Swapping :  a = %d   &   b = %d",a,b);
}

void Swap(int *a, int *b) {
int temp = *a;
     *a = *b;
     *b = temp;
}
  

Before Swapping:  a = 45   &   b = 20
After Swapping   :  a = 20   &   b = 45

  
Call by value - C++
  
 Source Code
  

  
    #include<iostream>
using namespace std;

class Swapper {
  public:
    void Swap(int a, int b);
};

void Swapper::Swap(int a, int b) {
int temp = a;
       a = b;
       b = temp;
    cout<< "Swapped Inside Swap() :  a = "<< a<< "  &  b = "<< b<< endl;
}

int main() {
int a, b;
Swapper object;
  cout<< "Enter the value of a:  ";
  cin>> a;
  cout<< "Enter the value of b:  ";
  cin>> b;
  system("cls");

  cout<< "Before calling Swap() :  a = "<< a<< "  &  b = "<< b<< endl;
  object.Swap(a,b);
  cout<< "\nBut not Swapped inside main() :  a = "<< a<< "  &  b = "<< b<< endl;

  return 0;
}

Enter the value of a:  12
Enter the value of b:  56
  
Before calling Swap()     :  a = 12   &   b = 56
Swapped Inside Swap() :  a = 56   &   b = 12
  
But not Swapped inside main() :  a = 12   &   b = 56

  
Call by reference - C++
  
 Source Code
  

  
#include<iostream>
using namespace std;

class Swapper {
  public:
    void Swap(int *a, int *b);
};

void Swapper::Swap(int *a, int *b) {
int temp = *a;
    *a = *b;
    *b = temp;
}

int main() {
int a, b;
Swapper object;
  cout<< "Enter the value of a:  ";
  cin>> a;
  cout<< "Enter the value of b:  ";
  cin>> b;
  system("cls");

  cout<< "Before Swapping:  a = "<< a<< "  &  b = "<< b<< endl;
  object.Swap(&a,&b);
  cout<< "After Swapping :  a = "<< a<< "  &  b = "<< b<< endl;

  return 0;
}

Before Swapping:  a = 20  &  b = 60
After Swapping   :  a = 60  &  b = 20