void select()
{
	FILE *fp,*ff;
	int i,n;
	if((fp=fopen("a.txt","w"))==NULL)
	{
		printf("file open error");
		exit(0);
	}
	printf("输入多少位学生的信息\n");
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
	printf("请输入学号:\n");
	scanf("%d",&student[i].id);
	fprintf(fp,"%d ",student[i].id);
	printf("请输入班级:\n");
	scanf("%d",&student[i].class);
	fprintf(fp,"%d ",student[i].class);
	printf("请输入姓名:\n");
	scanf("%s",&student[i].name);
	fprintf(fp,"%s ",student[i].name);
	printf("请输入开始上机时间（小时）:\n");
	scanf("%d",&student[i].time_beginhour);
	fprintf(fp,"%d ",student[i].time_beginhour);
	printf("请输入开始上机时间（分钟）:\n");
	scanf("%d",&student[i].time_beginminute);
	fprintf(fp,"%d ",student[i].time_beginminute);
	printf("请输入结束上机时间（小时）:\n");
	scanf("%d",&student[i].time_endhour);
	fprintf(fp,"%d ",student[i].time_endhour);
	printf("请输入结束上机时间（分钟）:\n");
	scanf("%d",&student[i].time_endminute);
	fprintf(fp,"%d\n",student[i].time_endminute);
    }
	if(fclose(fp))
	{
		printf("Can not close the file\n");
		exit(0);
	}
	ff=fopen("b.txt","w");
	fprintf(ff,"%d",i);/*存放学生人数*/ 
	fclose(ff);
	printf("保存成功");
}
void count()
{

	FILE *fp;
	int id,i=0,j,money;
		printf("请输入你的学号\n");
		scanf("%d",&id);
	if((fp=fopen("a.txt","r"))==NULL)
	{
		printf("file open error");
		exit(0);
	}
	while(!feof(fp))
	{
		fscanf(fp,"%d%d%s%d%d%d%d",&student[i].id,&student[i].class,&student[i].name,&student[i].time_beginhour,&student[i].time_beginminute,&student[i].time_endhour,&student[i].time_endminute);
		i++;
		j=i;
	}
	for(i=0;i<=j;i++)
	{
	if(student[i].id==id)
	{
	printf("学号；%d\n",student[i].id);
	printf("班级；%d\n",student[i].class);
	printf("姓名；%s\n",student[i].name);
	printf("开始上机时间；%d:%d\n",student[i].time_beginhour,student[i].time_beginminute);
	printf("结束上机时间；%d:%d\n",student[i].time_endhour,student[i].time_endminute);
	money=(student[i].time_endhour-student[i].time_beginhour)*60*m+(student[i].time_endminute-student[i].time_beginminute)*m;
    }
    }
    if(fclose(fp))
	{
		printf("Can not close the file\n");
		exit(0);
	}
	printf("本次上机的费用为:%d",money);
}
void add()
{
	int i;
	int n,j;
	printf("请输入要增加多少人的信息\n");
	scanf("%d",&n);
	FILE *fp,*ff;
	ff=fopen("b.txt","r");
	fscanf(ff,"%d",&i);
	fclose(ff);
	fp=fopen("a.txt","a");
	printf("请输入要增加的学生信息\n");
	for(j=1;j<=n;j++)
	{
    printf("请输入学号:\n");
    scanf("%d",&student[i+j].id);
	fprintf(fp,"%d ",student[i+j].id);
	printf("请输入班级:\n");
	scanf("%d",&student[i+j].class);
	fprintf(fp,"%d ",student[i+j].class);
	printf("请输入姓名:\n");
	scanf("%s",&student[i+j].name);
	fprintf(fp,"%s ",student[i+j].name);
	printf("请输入开始上机时间（小时）:\n");
	scanf("%d",&student[i+j].time_beginhour);
	fprintf(fp,"%d ",student[i+j].time_beginhour);
	printf("请输入开始上机时间（分钟）:\n");
	scanf("%d",&student[i+j].time_beginminute);
	fprintf(fp,"%d ",student[i+j].time_beginminute);
	printf("请输入结束上机时间（小时）:\n");
	scanf("%d",&student[i+j].time_endhour);
	fprintf(fp,"%d ",student[i+j].time_endhour);
	printf("请输入结束上机时间（分钟）:\n");
	scanf("%d",&student[i+j].time_endminute);
	fprintf(fp,"%d\n",student[i+j].time_endminute);
    }
	fclose(fp);
	printf("保存成功");
	ff=fopen("b.txt","w");
	fprintf(ff,"%d",i+n);
	fclose(ff);
}