用vector写学生管理系统，浏览模块无法输出结果

Question

#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
using namespace std;
struct stu
{
    char name[20];
    
    int score;
};

void makemenu()
{
    cout<<"---------学生成绩管理----------"<<endl;
    cout<<"1.录入功能"<<endl;
    cout<<"2.浏览功能"<<endl; 
    cout<<"3.删除功能"<<endl;
    cout<<"4.修改功能"<<endl;
    cout<<"5.查询功能"<<endl; 
    cout<<"6.退出系统"<<endl;
    cout<<"-----------------------------------"<<endl; 
}

long get_long()
{
    long input;
    char ch;
    while(scanf("%d", &input) != 1)
    {
        while((ch = getchar())!= '\n') 
            putchar(ch);
        cout<<"输入错误，请重新输入"<<endl; 
    }
    
    return input;}
    
    
void keydown()
{long m;
struct stu b;
vector<struct stu>vk;
vector<stu>::iterator it=vk.begin();
m=get_long();
switch(m)
    {
        
        case 1:cout<<"----【录入模块】----"<<endl;
        cin>>b.name>>b.score;
        vk.push_back(b);
        break;
        
        case 2:cout<<"----【浏览模块】----"<<endl;
    
        for(;it!=vk.end();it++)    
            {
                cout<<(*it).name<<' '<<(*it).score<<endl;
            }
        break;
            
        case 3:cout<<"----【删除模块】----"<<endl;
        
        break;
        
        case 4:cout<<"----【修改模块】----"<<endl;
        break;
        
        case 5:cout<<"----【查询模块】----"<<endl;
        break;
        
        case 6:cout<<"----【退出系统】----"<<endl;
              exit(0);
              break;
    }
}
int main()
{

while(1)
{
        makemenu();
        keydown();
        system("pause");
        system("cls");
}
}

Answer 1

vector vk;要放到全局变量。还要录入信息