Problem with pointer to string in C

Question

#include <stdio.h>

#define INCREMENT(x) ++x

int main()

{

    char *ptr = "GeeksQuiz";

    int x = 10;

    printf("%s  ", INCREMENT(ptr));

    printf("%d", INCREMENT(x));

    return 0;

}

// Output: eeksQuiz 11

My question: in that program, the pointer to "GeeksQuiz" is increased by 1, but i was taught that the pointer to an array (more specifically the pointer to the first element of an array) should be treated as a constant and such operation as ptr=(some value) or ptr++ is nonsense. Despite that, the program still run fine and output true results, why?

Answer 1

The ptr pointer can definitely be incremented to point to the second element in the char array and incrementing 10 gives 11.

Answer 2

It is not a pointer that can't be edited but a static array's pointer (ex: char a[25])