Passing Pointers to Functions In C++

// C++ program to change value of x
// by passing an argument to a function
// without a pointer
#include <iostream>
using namespace std;

void fun(int x) { x = 5; }

// Driver code
int main()
{
    int x = 9;
    cout << "value of x before calling fun: " << x << endl;
    fun(x);

    cout << "value of x after calling fun: " << x << endl;
    return 0;
}

// C++ program to change values of x
// by passing an argument to a function
// with a pointer
#include <iostream>
using namespace std;

void fun(int* ptr) { *ptr = 5; }

// Driver code
int main()
{
    int x = 9;
    cout << "value of x before calling fun: " << x << endl;
    fun(&x);

    cout << "value of x after calling fun: " << x << endl;
    return 0;
}

// C++ program to swap two values
// without passing pointer to
// swap function.
#include <iostream>
using namespace std;
void swap(int x, int y)
{
    int temp = x;
    x = y;
    y = temp;
}

// Driver code
int main()
{
    int a = 2, b = 5;
    cout << "values of a and b before swapping: " << a
         << " " << b << endl;
    swap(a, b);
    cout << "values of a and b after swapping: " << a << " "
         << b << endl;
    return 0;
}

// C++ program to swap two values
// without passing pointer to
// swap function.
#include <iostream>
using namespace std;
void swap(int* x, int* y)
{
    int temp = *x;
    *x = *y;
    *y = temp;
}

// Driver code
int main()
{
    int a = 2, b = 5;
    cout << "values of a and b before swapping: " << a
         << " " << b << endl;
    swap(&a, &b); // passing address of a and b
    cout << "values of a and b after swapping: " << a << " "
         << b << endl;
    return 0;
}

// C++ program to display element of
// array by passing argument to a
// function with pointer.
#include <iostream>
using namespace std;

void display(int* ptr, int n)
{
    for (int i = 0; i < n; ++i) {
        cout << *(ptr + i) << " ";
    }
}

int main()
{
    int arr[] = { 1, 2, 3, 4, 5 };
    int n = sizeof(arr) / sizeof(int);

    // ptr will store the address of first block of array
    int* ptr = arr;

    // passing argument to a function as pointer.
    display(ptr, n);

    return 0;
}