C++的Hello World错误

我开始学习C++,并尝试运行经典的Hello World程序:

#include 

using namespace std;

int main ()
{
  cout << "Hello, World!";
  return 0;
}

但是当我使用GCC在终端中编译它时,我总是得到错误:

Undefined symbols for architecture x86_64:
  "std::basic_string, std::allocator >::size() const", referenced from:
      std::__verify_grouping(char const*, unsigned long, std::basic_string, std::allocator > const&)in ccpe3DPY.o
  "std::basic_string, std::allocator >::operator[](unsigned long) const", referenced from:
      std::__verify_grouping(char const*, unsigned long, std::basic_string, std::allocator > const&)in ccpe3DPY.o
  "std::cout", referenced from:
      _main in ccpe3DPY.o
  "std::basic_ostream >& std::operator<<  >(std::basic_ostream >&, char const*)", referenced from:
      _main in ccpe3DPY.o
  "std::ios_base::Init::Init()", referenced from:
      __static_initialization_and_destruction_0(int, int)in ccpe3DPY.o
  "std::ios_base::Init::~Init()", referenced from:
      ___tcf_0 in ccpe3DPY.o
  "___gxx_personality_v0", referenced from:
      Dwarf Exception Unwind Info (__eh_frame) in ccpe3DPY.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

你能告诉我为什么吗？