Why can't I assign the int variable i to the int pointer *ip? They are both int

Why can't I assign the int variable i to the int pointer *ip? They are both int

I'm new to Java. I'm trying to learn the concept of pointer and reference. Could someone please explain to me why the code below is illegal? Why can't I assign the int variable i to the int pointer *ip? They are both int. I'm really struggling with the concept. Thanks in advance for any help!

int i = 0;    int *ip = i;  

Answer by VolAnd for Why can't I assign the int variable i to the int pointer *ip? They are both int

In case

 int *ip = i;  

you actually assign value 0 to pointer. I.e. ip has type int * - pointer to int, and it is not int. If you want assign 0 to pointer use

 int *ip = NULL; // good way  

or

 int *ip = (int *)i; // incorrect pointer initialization with explicit type conversion  

In general, assignment to pointer have to be NULL or address of allocated memory (allocated with new or malloc or address of existing variable taken with unary & operator), e.g.

 int *ip = NULL;   ip = &i; // address of variable   ip = malloc(sizeof(int)); // allocation in C style   ip = new int; // allocation in C++ style  

then value can be assigned to allocated memory with pointer as follows:

 *ip = i; // here pointer value (address) is not changed  

To see address (value of pointer) and pointed value test that statement:

 std::cout << "Adress " << ip << " contains value " << *ip << std::endl;  

Answer by SnG for Why can't I assign the int variable i to the int pointer *ip? They are both int

int *ip  

is a variable known as a pointer that could hold a memory address of a variable of type int. i is of type int, so to use the pointer correctly, type

int *ip = &i;  

which assigns the pointer ip to the memory address of i

Answer by Harpo Roeder for Why can't I assign the int variable i to the int pointer *ip? They are both int

You can like this:

int i = 0;  int* ip = 5;  *ip = i;  

Answer by Chaudhari Mahendra for Why can't I assign the int variable i to the int pointer *ip? They are both int

ip is a pointer and pointer must be hold the address of another variable.

int i = 0;  int *ip;  ip = &i;  

or

int *ip = &i;  

Answer by Asesh for Why can't I assign the int variable i to the int pointer *ip? They are both int

You have to either initialize that pointer or assign a valid memory address to it. This will assign the address of 'i' to ip

int *ip = &i;  

You could also do this:

int *ip = new int(12);  std::cout<<*ip<

Output:

12  

Fatal error: Call to a member function getElementsByTagName() on a non-object in D:\XAMPP INSTALLASTION\xampp\htdocs\endunpratama9i\www-stackoverflow-info-proses.php on line 72