30.改变学生结构体数组中的值

程序通过定义学生结构体变量，存储了学生的学号、姓名和3门课的成绩。所有学生数据均以二进制方式输出到文文件中。函数fun的功能是重写形参filename所指文件中最后的一个学生的数据，即用新的学生数据覆盖该学生原来的数据，其他学生的数据不变。

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#define N 5
typedef struct student
{
long sno;
char name[10];
float score[3];

}STU;
void fun(char *filename, STU n)
{
FILE *fp;
fp = fopen(filename, "rb+");
fseek(fp, -1L*(long)sizeof(STU), 2);
fwrite(&n, sizeof(STU), 1, fp);
fclose(fp);

}
int main()
{
STU t
= { {1001,"MaoChao",91,92,77},
{10002,"CaoKai",75,76,88},
{10003,"LiSi",85,70,78},
{10004,"FangFang",90,82,87},
{10005,"ZhangSi",95,80,88} },ss
;

STU n = { 10006,"ZhaoSan",55,70,68 };
int i, j;
FILE *fp;
fp = fopen("student,dat", "wb");
fwrite(t, sizeof(STU), N, fp);
fclose(fp);
printf("\nThe original data :\n\n ");
for (j = 0;j < N;j++)
{
printf("\nNo: %ld Name :%-8s Score: ", t[j].sno, t[j].name);
for (i = 0;i < 3;i++)
printf("%6.2f",t[j].score[i]);
printf("\n");
}
fun("student.dat", n);
printf("\nThe data after modifing :\n\n");
fp = fopen("student.dat", "rb+");
fread(ss, sizeof(STU), N, fp);
fclose(fp);
for (j = 0;j < N;j++)
{
printf("\nNo:%ld Name:%-8s Score:", ss[j].sno, ss[j].name);
for (i = 0;i < 3;i++)
printf("%6.2f", ss[j].score[i]);
printf("\n");
}
getchar();
return 0;

}