1)dialog data exchange (DDX) 

All dialog data functions are done with C++ code. There are 
no special resources or magic macros. The heart of the 
mechanism is a virtual function that is overridden in every 
dialog class that does dialog data exchange and validation. 
It is always found in this form:

 Copy Code
void CMyDialog::DoDataExchange(CDataExchange* pDX)
{
    CDialog::DoDataExchange(pDX);    // call base class

    //{{AFX_DATA_MAP(CMyDialog)
        <data_exchange_function_call>
        <data_validation_function_call>
    //}}AFX_DATA_MAP
}


2)dialog data validation (DDV)

DDX(DoDataExchange()
Is use To associate Control variable To Control ID.

DDV(DoDataValidation)
Is used to Set the range of control Value.

DDV - > Associate Single control with single variable.So
that we can define the properties for that associated variable.
DDX - > Associate Input Validation Function with Particular
variable.
for ex:
void DDV_Check(CDataExchange* dx, int DividerValue)

{
	if ( DividerValue< 0)
	{
	AfxMessageBox("Not Valid Input for Divider");
	dx->Fail();
	}
}
///Calling Function

//{{AFX_DATA_MAP(CDlg)
	 
	DDV_Check(dx, m_age);   // Our function

//}}AFX_DATA_MAP