[완료]visual studio 2010에서 api프로그램 질문입니다.

#include <windows.h>
 
ATOM RegisterMainWndClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow);
 
LRESULT CALLBACK MainWndProc(HWND hwnd, UINT message,
							 WPARAM wParam, LPARAM lParam);
 
static TCHAR gszAppName[] = TEXT("HelloWin");			
 
// WinMain 함수 부분
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
					 LPSTR lpCmdLine, int nCmdShow)
{
	MSG msg;
 
	if(!RegisterMainWndClass(hInstance))
		return -1;
	// WNDCLASS 등록	
 
	if(!InitInstance(hInstance, SW_SHOWNORMAL))
		return -1;
	// 인스턴스 초기화
 
 
	// 메시지 루프 부분
	while(GetMessage(&msg,NULL,0,0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
 
	return msg.wParam;
}
// WNDCLASS 등록 부분
ATOM RegisterMainWndClass(HINSTANCE hInstance)
{	
	WNDCLASS wndclass;			
 
	wndclass.style			= CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc	= MainWndProc;					
	wndclass.cbClsExtra		= 0;					
	wndclass.cbWndExtra		= 0;
	wndclass.hInstance		= hInstance;
	wndclass.hIcon			= LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor		= LoadCursor (NULL, IDC_ARROW);
	wndclass.hbrBackground	= (HBRUSH) GetStockObject (HOLLOW_BRUSH);	
	wndclass.lpszMenuName	= NULL;
	wndclass.lpszClassName	= gszAppName;
 
	if (!RegisterClass (&wndclass))
	{
		MessageBox (NULL, TEXT("This program requires Windows XP!"), gszAppName, MB_ICONERROR);
		return 0;
	}	
	return RegisterClass(&wndclass);
}
 
 
// 인스턴스를 초기화 하는 부분
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
	HWND		hwnd;
 
	hwnd = CreateWindow (gszAppName,
						L"The Hello Program",
						WS_OVERLAPPEDWINDOW,
						CW_USEDEFAULT,
						CW_USEDEFAULT,
						CW_USEDEFAULT,
						CW_USEDEFAULT,
						NULL,
						NULL,
						hInstance,
						NULL);
 
	ShowWindow (hwnd, nCmdShow);
	UpdateWindow (hwnd);
 
	return TRUE;
}
 
LRESULT CALLBACK MainWndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	HDC				hdc;
	PAINTSTRUCT		ps;
	RECT			rect;
	switch (message)
	{
	case WM_CREATE:
		return 0;
	case WM_PAINT:
		hdc = BeginPaint (hwnd, &ps);
		GetClientRect (hwnd, &rect);
		DrawText (hdc, L"Hello, Windows7!", -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
		EndPaint (hwnd, &ps);
		return 0;
 
	case WM_DESTROY:
		PostQuitMessage (0);
		return 0;
	}
 
	return DefWindowProc (hwnd, message, wParam, lParam);
}