read-only pages

#include <stdio.h>
#include <stdlib.h>

int main() {
        int i;
        int *a = malloc(409600000);
        int j = 0, k;

        for (i = 0; i < 5000; i++) {
                for (k = 0; k < 19; k++) {
                        j += 1024;
                        k ++;
                        a[j] = 1;
                }
                j += 1024;
        }

        printf("Pages allocated.\n");
        getchar();
        return 0;
}