程序代码：

#include<stdio.h>
#include<stdlib.h>
#define N 5
#define M 3
struct stu
{
    char name[10];
    int num;
   
    float score[3];
    float ave;
}stu[N];
void main()
{
    int i,j;
    float sum=0.0;
    FILE *fp;
    printf("请输入N=5个学生的信息:\n");
    for(i=0;i<N;i++)
    {
        printf("请输入第%d个学生的信息:\n",i+1);
        printf("name:\n");
        scanf("%s",stu[i].name);
        printf("NO.:\n");
        scanf("%d",&stu[i].num);
        for(j=0;j<M;j++)
        {
            printf("请输入第%d们成绩:\n",j+1);
            scanf("%f",&stu[i].score[j]);
            sum+=stu[i].score[j];
        }
        stu[i].ave=sum/M;

   
    }
    

   
    if((fp=fopen("E:\\stud.txt","wb"))==NULL)
    {
        printf("cannot open file\n");
        exit(0);
    }
//    fp=fopen("E:\\stud.txt","w");
    for(i=0;i<N;i++)
        if(fwrite(&stu[i],sizeof(struct stu),1,fp)!=1)
            printf("file write error\n");
        fclose(fp);

fp=fopen("stud.txt","rb");
for(i=0;i<N;i++)
{
    fread(&stu[i],sizeof(struct stu ),1,fp);
    printf("\n%s,%d,%.2f,%.2f,%.2f,%.2f\n",stu[i].name,stu[i].num,stu[i].score[0],stu[i].score[1],stu[i].score[2],stu[i].ave);
}
fclose(fp);


}