c语言实现排序求和，求平均

#include<stdio.h>
#define n 5
struct student
 {
   int num;
   char name[20];
   float score[3];
   float sum;
   float avg;
 };

 void main()
   {
     void input(struct student stu[]);
     void order(struct student stu[]);
     void print(struct student stu[]);
     struct student stu[n],*p=stu;
     /* stu[n]={{1001,"tom",{80,90,100},0,0},{1002,"jim",{80,80,80},0,0},{1003,"sau",{80,90,100},0,0},{1004,"jan",{80,80,80},0,0},{1005,"tian",{80,80,80},0,0}} ;
     p=stu;*/
     input(p);
     order(p);
     print(p);
     getch();
   }

 void input(struct student stu[])
    {
     int i;
     printf("please input the information of the students:sno name grade of math english physic\n");
     for(i=0;i<n;i++)