Question

C语言数据块读写

看看哪错了？运行后输入1遍就被退了出来，写入的数据只有前2个比较符合，中间还有些乱码。。从书上抄的，怎么还有错啊，？
#include<stdio.h>
#include<stdlib.h>
int main()
{
FILE *fp1;
int i;
struct stu
{
char name[15];
char num[6];
float score[2];
} student;
if((fp1=fopen("test.txt","wb"))==NULL)
{
printf("cannot open file");
exit(0);
}
printf("input data:\n");
for(i=0;i<2;i++)
{ scanf("%s%s%f%f",student.name,student.num,&student.score[0],&student.score[1]);
fwrite(&student,sizeof(student),1,fp1);
fclose(fp1);
if((fp1=fopen("text.txt","rb"))==NULL)
{
printf("cannot open file");
exit(0);
}
printf("out from file:\n");
for(i=0;i<2;i++)
{ fread(&student,sizeof(student),1,fp1);
printf("%s%s%7.2f%7.2f\n",student.name,student.num,student.score[0],student.score[1]);
}
fclose(fp1);
return 0;
}}
if((fp1=fopen("text.txt","rb"))==NULL)
{
printf("cannot open file");
exit(0);
}
这是什么意思啊？不能直接打开文件用fp1=fopen("text.txt","rb");么？

Answer 1

fopen函数完全可以，但为了确保文件是被打开，加了if判断，这是程序设计问题，而且这个函数有返回值

Answer 2

if((fp1=fopen("text.txt","rb"))==NULL)
{
printf("cannot open file");
exit(0);
}
确保文件成功地打开，否则用fp1=fopen("text.txt","rb");也是可以的。