#include<Stdio.h>
#include<stdlib.h>
struct student
{
    int age;
    int num;
    char sex;
}student1;
 save()
{
    FILE *fp;
    if((fp=fopen("D:\\334dd","wb"))==NULL)
    {
        printf("error");
        return(0);
    }
 if(fwrite(&student1,sizeof(struct student),1,fp)!=1)
     printf("file write error!");
 fclose(fp);

}
void main()
{
    printf("请输入数据！\n");
    scanf("%d,%d,%s",&student1.age,&student1.num,&student1.sex);

    printf("正在保存...\n");   
    save();

    system("cls");
    printf("保存成功！");

}

if((fp=fopen("D:\\334dd","wb"))==NULL)
if(fwrite(&student1,sizeof(struct student),1,fp)!=1)
 用二进制形式写进去的，用记事本打开就是乱码。

那该怎么打开？

用fprintf()格式化输入嘛