编译没问题，可能是非法内存访问，
void in()
 {
     int i,m=0;
     char ch[2];
     FILE *fp;
     if((fp=fopen("data","a+"))==NULL)
     {
         printf("系统出错，请与开发人员联系！\n");
         return;
     }
     while(!feof(fp))
     {
         if(fread(&stu[m],sizeof(struct student),1,fp)==1)
         m++;
     }
     fclose(fp);
     if(m==0)
          printf("无学生成绩记录!\n");
     else
     {
         system("cls");
         show();
     }
     if((fp=fopen("data","w+"))==NULL)
     {
         printf("系统出错，请与开发人员联系！\n");
         return;
     }
     printf("是否录入学生成绩，请按(y/n):");
     scanf("%s",ch);
     while(strcmp(ch,"Y")==0||strcmp(ch,"y")==0)
     {
         printf("请输入学生学号：");
         scanf("%d",&stu[m].num);
         for(i=0;i<m;i++)
             if(stu[i].num==stu[m].num)
            {
                printf("您输入的学号已经存在！");
                getch();
                fclose(fp);
                return;
             }
             printf("请输入学生姓名:");
             scanf("%s",&stu[m].name);
             printf("c语言:");
             scanf("%f",&stu[m].c);
             printf("高数:");
             scanf("%f",&stu[m].m);
             printf("英语:");
             scanf("%f",&stu[m].e);
             stu[i].sum=stu[m].c+stu[m].e+stu[m].m;
             if(fwrite(&stu[m],sizeof(struct student),1,fp)==1)
             {
                     printf("%s成绩录入成功!\n",stu[i].name);
                 m++;
             }
             else
             {
             printf("不能保存，请与开发人员联系！\n");
             }
     }
     fclose(fp);
 }

编译不了