How is it possible to save two data in the same memory location on C?

I’m learning C language, specifically pointers and I have this little question.

How is it possible to save two data in the same memory location on C? Look my code:

#include <stdio.h>

int main()
{
    const int y = 2;
    int *const ptr_y = &y;

    *ptr_y = 4;
    
    //Values
    printf("%d\n", y);
    printf("%d\n\n", *ptr_y);

    //Memory locations
    printf("%p\n", &y);
    printf("%p\n", ptr_y);

    return (0);
}

OUTPUT:
2
4

0x7ffeeb501788
0x7ffeeb501788

OUTPUT I EXPECT: 
4 
4 

0x7ffeeb501788 
0x7ffeeb501788 

I would like to know how this code works internally.

IMPORTANT: I am aware that the constant pointer is not correctly declared (const int *ptr_y).

>Solution :

You are not saving the data in two different locations, it’s the same location.

y is stored somewhere on the stack, that location has an address, ptr_y is a pointer and it contains that same memory address because you assigned it using address-of operator &:

int *const ptr_y = &y;

When you dereference ptr_y using * operator you are accessing the address stored in ptr_y which incidentally is the address of y, so it’s the same memory address, you are just accessing it in two different ways.

*ptr_y = 4 invokes undefined behavior because you cannot change the contents of a const variable.