Attempting to modify a constant pointer to non-constant data : const pointer « Pointer « C Tutorial

1. C Tutorial
2. Pointer
3. const pointer

1. ptr is a constant pointer to an integer that can be modified through ptr.
2. ptr always points to the same memory location.

#include <stdio.h>

int main()
{
   int x;
   int y;

   int * const ptr = &x; 

   *ptr = 7; /* allowed: *ptr is not const */
  // ptr = &y; /* error: ptr is const; cannot assign new address */

   return 0;

}