void read_unbuffered(int *password)
{
   int ch;
   int i;
   static const int color[]={0, 31, 34, 33, 35, 32, 39};

   setbuf(stdin, NULL);    
   echo_off();

   i = 0; 

   while ((ch = getchar()) != '\n')
   {      
      if(ch == '\b' && i != 0)
      {   
         fprintf(stderr, "\b\b  \b\b");        /*Don't mind this. As you can see below 
         i--;                                            after each entry it puts a space (for clarity), so I double backspace 
                                                           and double space to make up for this*/ 
      }

      else if((ch >= '1') && (ch <= '6') && i < 4)
      {
         // 1 is not '1'.  An ASCII 1, like you type in, is 49 in decimal.
         // An ASCII 9 is 57.
         // ASCII has them all in a row, so '5' - '0' == 5, etc.
         password[i] = ch-'0';

         // Use an array so you don't need umpteen different print statements
         fprintf(stderr, "\033[1;3;%d;49m%c \033[0m", color[ch-'0'], ch);

         i++;
      }
   }

   printf("\n");

   for(i = 0; i < 4; i++)           /*To see what is stored in the array*/
   {
      printf("%d ", password[i]);
   }

   echo_on();
}

int password_global[4];

int main(void)
{
        int password_local[4];

        // giving a pointer means no need to return anything -- the memory is modified directly.
        read_unbuffered(password_local); // modifies password_local
        read_unbuffered(password_global); // modifies password_global
}