程序2-1所示的SCRNSIZE程序展示了如何实作MessageBoxPrintf函数，该函数有许多参数并能像printf那样编排它们的格式。
程序2-1 SCRNSIZE SCRNSIZE.C /*--------------------------------------------------------------------------- SCRNSIZE.C -- Displays screen size in a message box (c) Charles Petzold, 1998 ----------------------------------------------------------------------------*/ #include <windows.h> #include <tchar.h> #include <stdio.h> int CDECL MessageBoxPrintf (TCHAR * szCaption, TCHAR * szFormat, ...) { TCHAR szBuffer [1024] ; va_list pArgList ; // The va_start macro (defined in STDARG.H) is usually equivalent to: // pArgList = (char *) &szFormat + sizeof (szFormat) ; va_start (pArgList, szFormat) ; // The last argument to wvsprintf points to the arguments _vsntprintf ( szBuffer, sizeof (szBuffer) / sizeof (TCHAR), szFormat, pArgList) ; // The va_end macro just zeroes out pArgList for no good reason va_end (pArgList) ; return MessageBox (NULL, szBuffer, szCaption, 0) ; } int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { int cxScreen, cyScreen ; cxScreen = GetSystemMetrics (SM_CXSCREEN) ; cyScreen = GetSystemMetrics (SM_CYSCREEN) ; MessageBoxPrintf ( TEXT ("ScrnSize"), TEXT ("The screen is %i pixels wide by %i pixels high."), cxScreen, cyScreen) ; return 0 ; }