想问一下为什么完成的子函数调用不出来？

Question

 #include<stdio.h>//学生结构体数组用来保存学生信息struct stu{    int num[11];       /*学号*/    char name[20];     /*姓名*/    int score[];      /*成绩*/};/*主菜单功能*/int show_window(){    printf("/*******************************************\n");    printf("*  the manage system of students' score     *\n");    printf("                                            \n");    printf("*--------description of program-------------\n");    printf("                                            \n");    printf("1.input data for students                   \n");    printf("                                            \n");    printf("2.output data for students                  \n");    printf("                                            \n");    printf("3.find data for students                    \n");    printf("                                            \n");    printf("4.insert data for students                  \n");    printf("                                            \n");    printf("5.sort data for students                    \n");    printf("                                            \n");    printf("6.alter data for students                   \n");    printf("                                            \n");    printf("7.delete data for students                  \n");    printf("                                            \n");    printf("8.get the fail students data                \n");    printf("                                            \n");    printf("9.average data for students                 \n");    printf("                                            \n");    printf("10.get above the average students data      \n");    printf("                                            \n");    printf("/*******************************************\n");}/*输入学生的学号，姓名，数学成绩，英语成绩，语文成绩分别存入数组num[],name[]*/int input_stu(){    int N;    printf("Please input the count of student number for N:\n");    scanf("%d",&N);    int i=0,num[11],name[20],score[N];    printf("Please input student's number and name and score:\n");    do{            scanf("%d,%c,%f",&num[i],&name[i],&score[N]);            i++;    }while((name[i-1]>=0)&&(i<N));    return i-1;}/*输出学生的信息*/int output_stu(){    int i,N,num[11],name[20],score[N];    for(i=0;i<N;i++)        printf("num[]=%d,name[]=%c,score[]=%f\n",&num[i],&name[i],&score[i]);}/*查找学生的信息*/int find_stu(){    int i,N,num[N],name[N],score[N],number;    printf("Please input the student'number:\n");    scanf("%d",&number); int value=number; int index=0; while(index>=0)    {  if(num[index]==value)  {   break;  }  else   index++; }        if(num[index]==value)        {            printf("%该学生信息存在，下标为：%d\n",value,index);        }        else {  printf("%d该学生信息不存在\n",value); }}/*插入学生信息*/int insert_stu(){}/*成绩排名*/int sort_stu(){}/*修改学生信息*/int alter_stu(){}/*删除学生信息*/int delete_stu(){}/*统计不及格学生*/int get_fail(){    int i,count=0,N,score[i],num[i],name[i];    printf("不及格的学生：\n");    for(i=0;i<N;i++);        if(score[i]<60)        {            count++;            printf("%101d%c-----%4f\n",num[i],name[i],score[i]);        }    return count;}/*求平均分*/int get_avg(){    int i,N;    int score[N];    int sum=0;    for(i=0;i<N;i++)        sum=sum+score[i];        return sum/N;}/*统计平均分以上的学生*/int get_above_avg(){    int i,N,count=0,score[i],num[i];    float avg;    /* 调用求平均分函数*/    int get_avg;    printf("在平均分以上的学生：\n");    for(i=0;i<N;i++)        if(avg<=score[i])    {        count++;        printf("%101d-----%4f\n",num[i],score[i]);    }    return count;}/*主函数*/int main(){    int select;    show_window();     /*输入菜单选项*/    printf("Please select 1-10 from show window\n");    scanf("%d",&select);    /*选择执行菜单*/    switch(select)    {        case 1:input_stu();break;        case 2:output_stu();break;        case 3:find_stu();break;        case 4:insert_stu();break;        case 5:sort_stu();break;        case 6:alter_stu();break;        case 7:delete_stu();break;        case 8:get_fail();break;        case 9:get_avg();break;        case 10:get_above_avg();break;        default:printf("error!");    }}

Answer 1

不能企图输入一个整数，然后通过这个整数来定义数组的长度大小，数组长度必须事先定义。