#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");


if ((isdigit(passCode[0])||(isdigit(passCode[1]))||(isdigit(passCode[2])))){
 hasDigit = true;
}


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

return 0;
}

White space replace.

1_

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

int main(void) {
 char passCode[3];

strcpy(passCode, "1 ");


if(passCode[1]== ' '){
 passCode[1]='_';
 };
 if(passCode[0]== ' '){
 passCode[0]='_';
 };


printf("%s\n", passCode);
 return 0;
}