MFC 를 배우기 전에 반드시 알아야 할 금전 창구 프로그램의 과정 코드

#include <windows.h>
//       
LRESULT CALLBACK MyWndProc (HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg)
	{
	case WM_DESTROY:
		PostQuitMessage (0);
		return 0;
	case WM_PAINT:
		PAINTSTRUCT ps;
		HDC hDC = BeginPaint (hwnd, &ps);
        Ellipse (hDC, 100, 100, 400, 400);
		EndPaint (hwnd, &ps);
		break;
	}
    return DefWindowProc (hwnd, uMsg, wParam, lParam);
}
//         
ATOM InitApplication (HINSTANCE hInstance)
{
	WNDCLASSEX wcs;
	wcs.cbSize = sizeof (wcs);
	wcs.cbWndExtra = 0;
	wcs.cbClsExtra = 0;
	wcs.hbrBackground = (HBRUSH)GetStockObject (WHITE_BRUSH);
	wcs.hCursor = LoadCursor (hInstance , IDC_CROSS);
	wcs.hIcon = LoadIcon (hInstance, IDI_INFORMATION);
	wcs.hIconSm = LoadIcon (hInstance, IDI_QUESTION);
	wcs.hInstance = hInstance;
	wcs.lpfnWndProc = MyWndProc;
	wcs.style = CS_VREDRAW | CS_HREDRAW;
	wcs.lpszMenuName = NULL;
	wcs.lpszClassName = "WinHello";
	return RegisterClassEx (&wcs);
}
//   、       
BOOL InitInstance (HINSTANCE hInstance, int nCmdShow)
{
	HWND hMainWnd = CreateWindowEx ( 0,
		                             "WinHello",
									 "MyWinHello",
									 WS_OVERLAPPEDWINDOW,
									 CW_USEDEFAULT,
									 CW_USEDEFAULT,
									 CW_USEDEFAULT,
									 CW_USEDEFAULT,
									 NULL,
									 NULL,
									 hInstance,
									 NULL);
	if (! hMainWnd)
		return FALSE;
	ShowWindow (hMainWnd, nCmdShow);
	UpdateWindow (hMainWnd);
	return TRUE;
}
//    ：        
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrecInstance, LPSTR lpCmdLine, int nShowCmd)
{
	if (! InitApplication (hInstance))
		return 0;
	if (! InitInstance (hInstance, nShowCmd))
		return 0;

	MSG msg;
	while (GetMessage (&msg, NULL, 0, 0))
	{
		TranslateMessage (&msg);
		DispatchMessage (&msg);
	}
	return msg.wParam;
}