Unlocking the Power of Pointers in C++

Understanding Pointers and Arrays

In C++, pointers are variables that hold the addresses of other variables. But what makes them truly powerful is their ability to store the addresses of cells in an array.

Let’s dive into an example to see how this works. Imagine we have an integer array arr and a pointer variable ptr. We can store the address of the first element of the array in ptr using the code ptr = arr;. Notice that we didn’t use &arr[0], because both are equivalent.

Pointing to Every Array Element

But what if we need to point to a specific element in the array using the same pointer ptr? Let’s say we want to point to the fourth element. If ptr points to the first element, then ptr + 3 will point to the fourth element.

We can access the elements using the single pointer, and the address between ptr and ptr + 1 differs by the size of the data type. For example, if ptr is a pointer to an int data type, the address difference is 4 bytes in a 64-bit operating system.

Example 1: C++ Pointers and Arrays

int arr[5] = {1, 2, 3, 4, 5};
int *ptr = arr;

cout << "Addresses of array elements:" << endl;
cout << &arr[0] << endl;
cout << &arr[1] << endl;
cout << &arr[2] << endl;
cout << &arr[3] << endl;
cout << &arr[4] << endl;

cout << "Using pointer ptr:" << endl;
cout << ptr << endl;
cout << ptr + 1 << endl;
cout << ptr + 2 << endl;
cout << ptr + 3 << endl;
cout << ptr + 4 << endl;

The output shows that we can access the addresses of the array elements using the pointer ptr.

Array Names as Pointers

In most contexts, array names decay to pointers. This means we can use pointers to access elements of arrays. However, it’s essential to remember that pointers and arrays are not the same. There are a few cases where array names don’t decay to pointers.

Example 2: Array Name Used as Pointer

int arr[5];
for (int i = 0; i < 5; i++) {
    cin >> *(arr + i);
}

for (int i = 0; i < 5; i++) {
    cout << *(arr + i) << endl;
}

In this example, we use the array name arr as a pointer to store and display the values entered by the user. We haven’t declared a separate pointer variable, but rather used the array name arr for the pointer notation. This is possible because the array name arr points to the first element of the array, making it act like a pointer.