Hello程序中主函数在什么地方?InitInstance();什么时候执行?

class CMyApp : public CWinApp
{
public:
virtual BOOL InitInstance();

};
class CMainWindow : public CFrameWnd
{
public:
CMainWindow();
protected:
afx_msg void OnPaint();
DECLARE_MESSAGE_MAP()
};
////////头文件Hello.h
#include <afxwin.h>
#include "Hello.h"
CMyApp myapp;
BOOL CMyApp::InitInstance()
{
m_pMainWnd=new CMainWindow;
m_pMainWnd->ShowWindow(m_nCmdShow);
m_pMainWnd->UpdateWindow();
return TRUE;
}
BEGIN_MESSAGE_MAP(CMainWindow,CFrameWnd)
ON_WM_PAINT()
END_MESSAGE_MAP()
CMainWindow::CMainWindow()
{
Create(NULL,_T("The hello Application"));
}
void CMainWindow::OnPaint()
{
CPaintDC dc(this);
CRect rect;
GetClientRect(&rect);
dc.DrawText(_T("Hello ,MFC"),-1,&rect,DT_SINGLELINE | DT_CENTER | DT_VCENTER);
}