一、test.cpp
include
using namespace std;
int main()
{
cout<<"hello"<
二、iostream位於/usr/include/c++/4.4，代碼如下：
// Standard iostream objects -*- C++ -*-
// Copyright (C) 1997, 1998, 1999, 2001, 2002, 2005, 2008, 2009
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// .
/** @file iostream
* This is a Standard C++ Library header.
*/
//
// ISO C++ 14882: 27.3 Standard iostream objects
//
#ifndef _GLIBCXX_IOSTREAM
#define _GLIBCXX_IOSTREAM 1
#pragma GCC system_header
#include
#include
#include
_GLIBCXX_BEGIN_NAMESPACE(std)//namespace {
/**
* @name Standard Stream Objects
*
* The header declares the eight standard stream
* objects. For other declarations, see
* http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt11ch24.html
* and the @link iosfwd I/O forward declarations @endlink
*
* They are required by default to cooperate with the global C library's
* @c FILE streams, and to be available during program startup and
* termination. For more information, see the HOWTO linked to above.
*/
//@{
extern istream cin; ///< Linked to standard input
extern ostream cout; ///< Linked to standard output
extern ostream cerr; ///< Linked to standard error (unbuffered)
extern ostream clog; ///< Linked to standard error (buffered)
#ifdef _GLIBCXX_USE_WCHAR_T
extern wistream wcin; ///< Linked to standard input
extern wostream wcout; ///< Linked to standard output
extern wostream wcerr; ///< Linked to standard error (unbuffered)
extern wostream wclog; ///< Linked to standard error (buffered)
#endif
//@}
// For construction of filebuffers for cout, cin, cerr, clog et. al.
static ios_base::Init __ioinit;
_GLIBCXX_END_NAMESPACE }
#endif /* _GLIBCXX_IOSTREAM */
說明cout是類ostream的實例，並且位於std這個命名空間下，所以要using namespace std;
cout<<是ostream類的運算符重載
