C | Storage Classes and Type Qualifiers | Question 19

#include <stdio.h>
int main()
{
    int x = 5;
    int * const ptr = &x;
    ++(*ptr);
    printf("%d", x);

    return 0;
}

(A) Compiler Error
(B) Runtime Error
(C) 6
(D) 5

Answer: (C)
Explanation: See following declarations to know the difference between constant pointer and 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.
Therefore 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 incrementing value pointed by ptr.

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