请教个问题

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
struct ifm
{
int age;
char name[20];
int year;
int month;
int day;
char xing[10];
int classic;
};
struct ifm stu;
int main(void)
{
FILE *pp;
int i,a;
pp=fopen("SAVE.txt","w");
printf("你想储存几个人的信息:");
scanf("%d",&i);
if(i>0)
{
for(a=0;a<i;a++)
{
printf("这是第%d个人:\n",a+1);
printf("他(她)的名字:");
scanf("%s",&stu.name);
fprintf(pp,"名字:%s\n",stu.name);
printf("他(她)的年龄:");
scanf("%d",&stu.age);
fprintf(pp,"年龄:%d\n",stu.age);
num:
{
printf("他(她)的出生年份:");
scanf("%d",&stu.year);
printf("他(她)的出生月份:");
scanf("%d",&stu.month);
printf("他(她)的出生日期:");
scanf("%d",&stu.day);
}
if(stu.month<=12&&stu.day<=31)
fprintf(pp,"生日:%d--%d--%d\n",stu.year,stu.month,stu.day);
else
{printf("错误!\n");goto num;}
printf("他(她)的性别:");
scanf("%s",&stu.xing);
fprintf(pp,"性别:%s\n",stu.xing);
printf("他(她)的班别(九年级):");
scanf("%d",&stu.classic);
fprintf(pp,"班别:初三(%d)班\n",stu.classic);
printf("---------------分割线-----------------\n");
fprintf(pp,"---------------分割线-----------------\n");
}
}
fclose(pp);
system("notepad.exe SAVE.txt");
system("pause");
return 0;
}我想测试文本里是否空字符，代码怎么写？？？？？