有关数字类型，谁能帮帮我哪错了，我要疯了

6 ，8, 10 行用else if

/**
 * @file number.c
 *
 * @brief
 * @author  Zhang Jianfa
 * @copyright (C) 2021zhangjianfa. All rights reserved.
 * @date    2021-10-13
 */
#include <stdio.h>

int main(int argc, char **argv)
{
  char ch = 0;
  scanf("%c", &ch);
  if(ch >= 'a' && ch <= 'z')
     printf("lower\n");
  else if(ch >= 'A' && ch <= 'Z')
     printf("upper\n");
  else if(ch >= '1' && ch <= '9')
     printf("digit\n");
  else
     printf("other\n");
}

root@seven:~/workspace/test/25.answer# gcc number.c
root@seven:~/workspace/test/25.answer# ./a.out
a
lower
root@seven:~/workspace/test/25.answer# ./a.out
1
digit
root@seven:~/workspace/test/25.answer# ./a.out
d^H^C
root@seven:~/workspace/test/25.answer# ./a.out
D
upperr