#include<stdio.h>
main()
{
char n;
printf("请输入一个字符:");
scanf("%c",&n);
if(n>='A'&&n<='Z')
   printf("A\n");
else
   if(n>='a'&&n<='z')
      printf("a\n");
   else
      if(n>='0'&&n<='9')
         printf("0\n");
      else
         printf("#\n");
}
这样就对了！