about “int const *p” and “const int *p ”

Question

#include 
using namespace std;

int main(int argc, char* argv[])
{
    int i1 = 0;
    int i2 = 10;

    const int *p = &i1;
    int const *p2 =          


        

Answer 1

const int *p = &i1;
int const *p2 = &i1;

These both declare non-const pointers to const data.

That is, using p, you cannot change the data it points to. However, you can change the pointer itself, for example, by assigning as p = &i2 which is legal. But *p = 87987 is illegal, as the data p points to is const!

--

int * const p = &i1;

This declares const pointer to non-const data. That is, p=&i2 is illegal, but *p = 98789 is legal.

--

const int * const p = &i1;

This declares const pointer to const data. That is, now both p=&i2 and *p=87897 are illegal.