#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define LIMIT 80
void ToUpper(char *);
int PunctCount(const char*);

int mian(void)
{
    char line[LIMIT];

    puts("Please enter a line:");
    gets(line);
    ToUpper(line);
    puts(line);
    printf("That line has %d punctuation characters.\n", PunctCount(line));

    system("pause");
    return 0;


}

void ToUpper(char * str)
{
    while (*str)
    {
        *str = toupper(*str);
        str++;

    }
}
int PunctCount(const char *str)
{
    int ct = 0;
    while (*str)
    {
        if (ispunct(*str))
            ct++;
    }
    return ct;
}

1>------ 已启动生成: 项目: U, 配置: Debug Win32 ------
1>  YT TR.c
1>d:\编程文件\c primer plus\u\u\yt tr.c(14): warning C4013: “gets”未定义；假设外部返回 int
1>MSVCRTD.lib(exe_main.obj) : error LNK2019: 无法解析的外部符号 _main，该符号在函数 "int __cdecl invoke_main(void)" (?invoke_main@@YAHXZ) 中被引用
1>D:\编程文件\c primer plus\U\Debug\U.exe : fatal error LNK1120: 1 个无法解析的外部命令
========== 生成: 成功 0 个，失败 1 个，最新 0 个，跳过 0 个 ==========

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#define LIMIT 80
void ToUpper(char *);
int PunctCount(const char *);

int mian(void)
{
    char line[LIMIT];

    puts("Please enter a line:");
    gets(line);
    ToUpper(line);
    puts(line);
    printf("That line has %d punctuation characters.\n", PunctCount(line));

    system("pause");
    return 0;


}

void ToUpper(char * str)
{
    while (*str)
    {
        *str = toupper(*str);
        str++;

    }
}
int PunctCount(const char *str)
{
    int ct = 0;
    while (*str)
    {
        if (ispunct(*str))
            ct++;
        str++;
    }
    return ct;
}

41行少了一句,抱歉!

main 写错了

额,怪我!!!!!