C语言fopen_s读写结构体

#include "stdafx.h"
#include <fstream>
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
typedef struct _MyDataTime {
    int  Index;//保留
    int  Year;         //年，这个日期为班次开始时的日期
    int  Month;        //月
    int  Day;          //日
} MyDataTime;

int main()
{
    MyDataTime mydatetime, mydatetime1;
    mydatetime.Day = 1;
    mydatetime.Index = 2;
    mydatetime.Month = 3;
    mydatetime.Year = 4;
    FILE *fp;
    errno_t err = fopen_s(&fp, "D://1.TXT", "w"); //读取文件数据
    cout << err << endl;
    fwrite(&mydatetime, sizeof(MyDataTime),1 ,fp);
    fclose(fp);
    err = fopen_s(&fp, "D://1.TXT", "r"); //读取文件数据
    fread(&mydatetime1, sizeof(MyDataTime),1, fp);
    cout << mydatetime1.Day << mydatetime1.Index << mydatetime1.Month << mydatetime1.Year;
    fclose(fp);
}