#include<iostream>
int main()
{
using namespace std;
cout<<"Enter the a:";
int a;
cin>>a;
int b;

for(b=a;b;b--)
cout<<"b="<<b<<"\n";
cout<<"mow a is"<<b<<"\n";
return 0;
}

Compiling...
jianjian.cpp
Linking...
jianjiian2.obj : error LNK2005: _main already defined in jianjian.obj
Debug/jianjian.exe : fatal error LNK1169: one or more multiply defined symbols found
执行 link.exe 时出错.

jianjian.exe - 1 error(s), 0 warning(s)