VC里面 %.

在调试窗口输出信息
在你编译和运行debug版的程序时从VC的Debug窗口输出信息
你就当一个全局变量吧.实际也是,不过只在DEBUG版时才有.
和TRACE差不多,只不过TRACE用的是printf 的参数格式.
afxDump重载了<<.

Provides basic object-dumping capability in your application.
CDumpContext afxDump;
Remarks
afxDump is a predefined CDumpContext object that allows you to send CDumpContext information to the debugger output window or to a debug terminal. Typically, you supply afxDump as a parameter to CObject::Dump.
Under Windows NT and all versions of Windows, afxDump output is sent to the Output-Debug window of Visual C++ when you debug your application.
This variable is defined only in the Debug version of MFC. For more information on afxDump, see Debugging MFC Applications. Technical Note 7 and Technical Note 12 contain additional information.
Note This function works only in the Debug version of MFC.
Example
// example for afxDump
CPerson myPerson = new CPerson;
// set some fields of the CPerson object...
//..
// now dump the contents
#ifdef _DEBUG
afxDump << \"Dumping myPerson:\\n\";
myPerson->Dump( afxDump );
afxDump << \"\\n\";
#endif