C和指针 13章练习题算是从书上转载的吧

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
//计算从标准输入的几类字符的百分比,是书上的答案

int is_not_print( int ch )//避免了主循环处理特殊情况的需要
{
        return !isprint( ch);
}
//用于区分每种类型的分类函数的跳转表

static int ( *test_func[] )( int ) =
{
iscntrl,
isspace,
isdigit,
islower,
isupper,
ispunct,
is_not_print
};
#define N_CATEGORIES\
   (sizeof( test_func)/ sizeof( test_func[ 0 ] ) )
   //每种类型名字
char *label [] =
{
        "control",
        "whitespace",
        "digit",
        "lower case",
        "upper case",
        "punctuation",
        "non_printable"
};
int count[ N_CATEGORIES ];
int total;

int main()
{
    int ch;
    int category;
    //读取和处理每个字符
    while( ( ch = getchar()) !=  EOF )//这里就是需要回车换行，ctrl+z再回车
          {
                  total += 1;
                  //为这个字符调用每个测试函数，结果为真，增加对应计数器的值
                  for( category = 0; category < N_CATEGORIES;category += 1 )
                        {
                                if( test_func[category](ch))
                                        count[category]+=1;
                        }
          }
          //打印结果
          if( total == 0 )
          {
                  printf("没有字符");

          }
          else
          {
                  for( category = 0; category < N_CATEGORIES; category += 1 )
                  {
                          printf( "%3.0f%% %s characters\n", count[ category ]*100.0/total,label[ category]);
                  }
          }
    return 0;
}