哪位过路的大佬帮忙看一下我的程序？

#include<bits/stdc++.h>
#include<cstring>
using namespace std;
struct student
{
    string name;//姓名 
    char sex;//性别 
    float score;//学分 
    int birthday;//生日 
}a[100];
int main()
{
    int num,i=0;//i表示第几个学生 
    cout<<"Please input the following num to run the program."<<endl;
    cout<<"1.add student"<<endl;//新添加学生信息 
    cout<<"2.delete last student"<<endl;//删除最后一个学生信息 
    cout<<"3.display student list"<<endl;//打印输出当前系统含有的学生信息 
    cout<<"4.save the student list to the the database"<<endl;//存储学生信息至数据库 覆盖（可以使用database.txt模拟） 
    cout<<"5.read the student list from the database"<<endl;//从数据库读取学生信息更新当前学生信息内容 
    cout<<"6.exit the program"<<endl<<endl;//退出程序 
    cout<<"Input num:";
    for(;;)
    {
        cin>>num;
        switch(num)
        {
            case 1:
                if(i==100)
                {
                    cout<<"学生信息已满！"<<endl;
                    cout<<"Input num:";
                    break;
                }
                else
                {
                    cout<<"Enter name>";
                    cin>>a[i].name >>a[i].sex >>a[i].score >>a[i].birthday ;
                    i++;
                    cout<<"Input num:";
                    break;
                }
            case 2:
                if(i==0)
                {
                    cout<<"当前还未有学生信息！请按1输入学生信息！"<<endl;
                    cout<<"Input num:";
                    break;
                }
                else
                {
                    a[i-1].name="";
                    a[i-1].sex =' ';
                    a[i-1].score =NULL;
                    a[i-1].birthday =NULL;
                    i--;
                    cout<<"Input num:";
                    break;
                }
            case 3:
                if(i==0)
                {
                    cout<<"当前没有任何学生信息！请按1添加学生信息！"<<endl;
                    cout<<"Input num:";
                }
                else
                    {
                    for(int n=0;n<i;n++)
                    {
                        cout<<a[n].name<<" ";
                        cout<<a[n].sex <<" ";
                        cout<<a[n].score <<" ";
                        cout<<a[n].birthday <<endl;
                    }
                    cout<<"Input num:";
                }
                break;
            case 4:
                freopen("学校学生管理软件.out","w",stdout);
                for(int n=0;n<i;n++)
                {
                    cout<<a[n].name<<" ";
                    cout<<a[n].sex <<" ";
                    cout<<a[n].score <<" ";
                    cout<<a[n].birthday<<endl;
                }
                fclose(stdout);
                cout<<"Input num:";
                break;
            case 5:
                cout<<freopen("学校学生管理软件.out","r",stdin)<<endl;
                fclose(stdin);
                cout<<"Input num:";
                cin>>num;
                break;
            case 6:
                return 0;
        }   
    }
}```
附：in文件内容为：Bob b 98 20070821