Which is the correct syntax to declare constant pointer?

In C and C++, you can declare a constant pointer in multiple ways, depending on what you want to be constant: the pointer itself or the value it points to. The correct syntax depends on the intention:

1. To declare a pointer that cannot change the value it points to (the data is constant), but the pointer can point to another location, you use:

const int *ptr;

```

or

```c

int const *ptr;

Both declarations ensure that the integer value `ptr` points to cannot be changed through this pointer.

2. To declare a pointer that cannot change the address it points to (the pointer is constant), but the data it points to can be changed, you use:

“`c

int *const ptr;

Here, `ptr` must be initialized at the point of declaration, and it cannot point to a different integer later.

3. To declare a constant pointer to a constant value (neither the pointer can change the address it points to, nor can the data it points to be changed through this pointer), you use:

“`c

const int *const ptr;

“`

or

“`c

int const *const ptr;

In all of these cases, `ptr` should be initialized either at declaration or before being used.