C++ Pointers in a Nutshell

Pointers are one of the most confusing elements of C++ language. So I wanted to give a brief explanation.

Photo by Artem Beliaikin on Unsplash

Let’s start by defining two variables.

int x = 5;
int y = x;

So here we defined an integer x and assigned value of 5 to it. Then we defined y and assigned x as the value of it. So now we have two variables which have different memory locations. They both have the same value.

In C++, there is another type called pointer which does not carry the value but points the address of value by the memory location.

Let’s define a pointer now.

int* ptr;

This line defines a pointer named ptr and it is a pointer of int.

Now let’s define the address of x to this pointer.

ptr = &x;

Ptr now holds the address of x. Now let’s define another line to use the address that our pointer holds.

y = *ptr;

Now when we print the value of y we expect to see value 5 since we assigned the value that is held by the address our pointer points.

An Example:

int main()
{
    int x {12};
    int y {3456};
    int* ptr = &x;
    std::cout << *ptr << std::endl;
    x = 789;
    std::cout << *ptr << std::endl;
    ptr = &y;
    std::cout << *ptr << std::endl;
    return 0;
}

This program will output

12
789
3456

The asterisk (*) de-references the pointer to the value it points and we see the correct values after each update.