c语言的问题，求大神的指导

Question

#include"stdio.h"
#include"stdlib.h"
struct stu
{ char name[10];
unsigned no,age;
};
void main()
{
struct stu *s;
FILE *fp;
scanf("%s%d%d",s->name,&s->no,&s->age);
fprintf(fp,"%s%d%d",s->name,&s->no,&s->age);
if((fp=fopen("stu.txt","w"))==NULL)
{ printf("cannot open file");
exit(1);}
fclose(fp);
if((fp=fopen("stu.txt","r"))==NULL)
{ printf("cannot open file");
exit(1);}

fscanf(fp,"%s%d%d",s->name,&s->no,&s->age);
printf("%s%d%d",s->name,s->no,s->age);
fclose(fp);
}成功创建了文本，但是无法把我输入的东西输入到文本上

Answer 1

struct stu *s;
没有创建 s就，直接使用，因此出现异常