一个简单的用C编写的学生成绩系统

student.h
#include<stdio.h>
#include<string.h>
#define MaxSize 50
struct student{
int num;
char name[10];
int computer,english,math,sum;
double average;
};
extern void search_student(struct student students[]);
extern void modify(struct student students[]);
extern void new_student(struct student students[]);
extern void output_student(struct student students[]);
extern void averagesort(struct student students[]);
extern void numsort(struct student students[]);

student_system.c
#include"student.h"
#include"input_output.c"
#include"aver_sort.c"
#include"modify.c"
int Count=0;
void main(){
struct student students[MaxSize];
new_student(struct student students);
output_student(struct student students);
sort(struct student students);
output_student(struct student students);
modify(struct student students);
output_student(struct student students);
}

modify.c
E:\Microsoft Visual Studio\MyProjects\student\modify.c(5) : warning C4013: 'printf' undefined; assuming extern returning int
E:\Microsoft Visual Studio\MyProjects\student\modify.c(6) : warning C4013: 'scanf' undefined; assuming extern returning int
E:\Microsoft Visual Studio\MyProjects\student\modify.c(12) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(12) : error C2037: left of 'num' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(16) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(16) : error C2037: left of 'math' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(18) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(18) : error C2037: left of 'english' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(20) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(20) : error C2037: left of 'computer' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(35) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(35) : error C2037: left of 'num' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(40) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(40) : error C2037: left of 'num' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(41) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(41) : error C2037: left of 'name' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(42) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(42) : error C2037: left of 'math' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(43) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(43) : error C2037: left of 'english' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(44) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(44) : error C2037: left of 'computer' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(45) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(45) : error C2037: left of 'sum' specifies undefined struct/union 'student'
E:\Microsoft Visual Studio\MyProjects\student\modify.c(46) : error C2036: 'struct student *' : unknown size
E:\Microsoft Visual Studio\MyProjects\student\modify.c(46) : error C2037: left of 'average' specifies undefined struct/union 'student'

我感觉我问题不多，但都是挺严重的问题，各路大神帮帮忙，小女子在此先谢过了

在线等到12点。。。
快来人呀

算了，我还是睡了
晚安

其实网上一大堆