C语言编程中编译运行正常，但是这一部分的功能不能正常使用怎么办

/**
**录入学生信息
*/
void in()
{
int i,m=0;
char ch[2];
FILE *fp;
if((fp=fopen("data.txt","a+"))==NULL)
{
printf("文件不存在！\n");
return;
}
while(!feof(fp))
{
if(fread(&stu[m],LEN,1,fp)==1)
{
m++;
}
}
fclose(fp);
if(m==0)
{
printf("文件中没有记录！\n");
}
else
{
show();
}
if((fp=fopen("data.txt","wb"))==NULL)
{
printf("文件不存在！\n");
return;
}
printf("输入学生信息（y/n):");
scanf("&s",ch);
while(strcmp(ch,"Y")==0||strcmp(ch,"y")==0)
{
printf("number:");
scanf("%d",&stu[m].num);
for(i=0;i<m;i++)
if(stu[i].num==stu[m].num)
{
printf("number已经存在，按任意键继续！");
getch();
fclose(fp);
return;
}
printf("name:");
scanf("%s",stu[m].name);
printf("elective:");
scanf("%lf",&stu[m].elec);
printf("experiment:");
scanf("%lf",&stu[m].expe);
printf("required course:");
scanf("%lf",&stu[m].requ);
stu[m].sum=stu[m].elec+stu[m].expe+stu[m].requ;
if(fwrite(&stu[m],LEN,1,fp)!=1)
{
printf("不能保存！");
getch();
}
else
{
printf("%s 被保存！\n",stu[m].name);
m++;
}
printf("继续？(y/n):");
scanf("%s",ch);
}
fclose(fp);
printf("OK!\n");
}