Constant pointer Vs a pointer to a constant.

int * const ptr —> ptr is constant pointer. You can change the value at the location pointed by pointer p, but you can not change p to point to other location. int const * ptr —> ptr is a pointer to a constant. You can change ptr to point other variable. But you cannot change the value pointed by ptr.


int * const ptr :

int main()

{

    int x = 5;

    int * const ptr = &x;

    ++(*ptr);

    printf("%d", x);

   

    return 0;

}

Output : 6




above program works well because we have a constant pointer and we are not changing ptr to point to any other location. We are only icrementing value pointed by ptr










int const * ptr




int main()

{

    int x = 5;

    int const * ptr = &x;

    ++(*ptr);

    printf("%d", x);

   

    return 0;

}




Output: Compiler Error




In the above program, ptr is a pointer to a constant. So the value pointed cannot be changed

#include<stdio.h> int main() {   typedef static int *i;   int j;   i a = &j;   printf("%d", *a);   return 0; }

(A) Runtime Error
(B) 0
(C) Garbage Value
(D) Compiler Error


Answer: (D)

Explanation: Compiler Error -> Multiple Storage classes for a. In C, typedef is considered as a storage class. The Error message may be different on different compilers