Pointer To Const

A pointer to const allows reading through the pointer while protecting the pointed-to value from writes through that pointer.

pointer_to_const.c

#include <stdio.h>

int main(void) {
    int first = ;
    int second = 6;
    int useSecond = ;
    const int *ptr = &first;

    if (useSecond) {
        ptr = &second;
    }

    printf("read=%d\n", *ptr);
    return 0;
}

#include <stdio.h>

int main(void) {
    int first = ;
    int second = 6;
    int useSecond = ;
    const int *ptr = &first;

    if (useSecond) {
        ptr = &second;
    }

    printf("read=%d\n", *ptr);
    return 0;
}

#include <stdio.h>

int main(void) {
    int first = ;
    int second = 6;
    int useSecond = ;
    const int *ptr = &first;

    if (useSecond) {
        ptr = &second;
    }

    printf("read=%d\n", *ptr);
    return 0;
}

#include <stdio.h>

int main(void) {
    int first = ;
    int second = 6;
    int useSecond = ;
    const int *ptr = &first;

    if (useSecond) {
        ptr = &second;
    }

    printf("read=%d\n", *ptr);
    return 0;
}

#include <stdio.h>

int main(void) {
    int first = ;
    int second = 6;
    int useSecond = ;
    const int *ptr = &first;

    if (useSecond) {
        ptr = &second;
    }

    printf("read=%d\n", *ptr);
    return 0;
}

#include <stdio.h>

int main(void) {
    int first = ;
    int second = 6;
    int useSecond = ;
    const int *ptr = &first;

    if (useSecond) {
        ptr = &second;
    }

    printf("read=%d\n", *ptr);
    return 0;
}

const pointee `const int *ptr` means the `int` cannot be changed through `ptr`.

reassign pointer The pointer itself can still be changed to read a different object.