```#include
#include
#define N 5
/*309-1.（1）计算并保存平均成绩。根据键盘输入，计算出平均成绩，
将原有数据和计算出的平均分数存储在磁盘文件student.txt中。详见P309，4（1）。*/
struct student
{
int num;
char name[20];
int score[3];
};
struct student st[N];
int main()
{
int i,sum1,sum2,sum3;
FILE *fp1;
fp1=fopen("student.txt","w");
for(i=0;i<N;i++)
{
fscanf(fp1,"%d%s%d%d%d",&st[i].num,st[i].name,&st[i].score[0],&st[i].score[1],&st[i].score[2]);
sum1+=st[i].score[0];
sum2+=st[i].score[1];
sum3+=st[i].score[2];
}
fscanf(fp1,"%5.2f%5.2f%5.2f",&sum1/N,&sum2/N,&sum3/N);
fclose(fp1);
return 0;
}
