程序代码：

#include "stdafx.h"
#include<process.h>
#include<stdio.h>
#include<Windows.h>
int g_bstop = false;
unsigned int __stdcall fun(void* )
{
    int a = 0;
    while(1)
    {           
        if(!g_bstop)printf("\r%d",a++);
        Sleep(200);
    }
    return 0;
}
int main()
{
    _beginthreadex(0,0,fun,0,0,0);
    while('\n'==getchar())
    {
        g_bstop ^= true;
    }
}