Two questions about basic C programs

Here’s how you would use a for loop;

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <ctype.h>

int main(void) {
   bool hasDigit;
   char passCode[50];

   hasDigit = false;
   strcpy(passCode, "abc");

   /* Your solution goes here  */
   for (int i=0; passCode[i]; i++)
       if (isdigit(passCode[i]))
           hasDigit = true;

   if (hasDigit) {
      printf("Has a digit.\n");
   }
   else {
      printf("Has no digit.\n");
   }

   return 0;
}