main函数形参--int argc char *argv[]/char **argv

//主函数main使用两个值作为实参，并输出它们的和
#include<iostream>
using namespace std;
int main(int argc,char **argv)//与int main(int argc,char *argv[])等价
{
  //检查命令行参数
  if(argc!=3){
  cout<<"You should use three arguments!"<<endl;
  return -1;
  }
  cout<<"Summation of "<<argv[1]<<" and "<<argv[2]<<" is "
  <<(atof(argv[1])+atof(argv[2]))<<endl;
  return 0;
}

1.main 函数实参 

2.函数运行结果