“File could not be opened”的问题

我想用C++编写一个输出电子邮件系列地址的程序到clinet.dat文件夹里，自认为代码没问题，可是运行就显示

“File could not be opened”现讲代码贴示如下，希望各位帮我看看八，菜鸟小弟在此谢过！！！

#include <iostream>

using std::cout;

using std::cin;

using std::ios;

using std::cerr;

using std::endl;

#include <fstream>

using std ::ofstream;

#include <cstdlib>

int main()

{

ofstream outClientFile ( "clients.dat, ios::out");

if (!outClientFile)

{

cerr<<"File could not be opened."<<endl;

exit ( 1 );

}

while ( 1 )

{

for (int i=1;i<=300;i++)

{

outClientFile <<"0372"<<i<<"@fudan.edu.cn;\n"<<endl;

cout<<"?";

}

}

return 0;

}