求指点， error LNK2001: unresolved external symbol _main
#ifndef STOCK1_H
#define STOCK1_H

class Stock
{
private:
char company[30];
int shares;
double share_val;
double total_val;
void set_tot();
public:
Stock();
Stock(const char*co,int n=0,double pr=0.0);
~Stock();
void buy(int num,double price);
void sell(int num,double price);
void update(double price);
void show();
};

#endif




#include<iostream>
#include<cstring>
#include"stock1.h"

Stock::Stock()
{
std::cout<<"Default constructor called\n";
strcpy(company,"no name");
shares=0;
share_val=0.0;
total_val=0.0;
}

Stock::Stock(const char*co,int n,double pr)
{
std::cout<<"Constructor using "<<co<<"called\n";
strncpy(company,co,29);
company[29]='\0';

if(n<0)
{
std::cerr<<"Number of shares can't be negative;"
<<company<<" shares set to 0.\n";
shares=0;
}
else
shares=n;
share_val=pr;
set_tot();
}

Stock::~Stock()
{
std::cout<<"Bey, "<<company<<"\n";
}



void Stock::buy(int num,double price)
{
if (num<0)
{
std::cerr<<"Number of shares purchased can't be negative."
<<"Transaction is aborted.\n";
}
else
{
shares+=num;
share_val=price;
set_tot();
}
}

void Stock::sell(int num,double price)
{
using std::cerr;
if (num<0)
{
cerr<<"Number of shares sold can't be negative."
<<"Transaction is aborted.\n";
}
else
{
shares-=num;
share_val=price;
set_tot();
}
}

void Stock::update (double price)
{
share_val=price;
set_tot();
}

void Stock::show()
{
using std::cout;
using std::endl;
cout<<"Company:"<<company
<<"Share: "<<shares<<endl
<<"Share Price: $"<<share_val
<<"Total Worth: $"<<total_val<<endl;
}

void Stock::set_tot()
{
total_val=shares*share_val;
}


[解决办法]
main函数在哪里？

[解决办法]
写个main函数