#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("HelloWin") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW  ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_EXCLAMATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (LTGRAY_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {    // UNICODE-Compilierung ist die einzige realistische Fehlermöglichkeit 
          MessageBox (NULL, TEXT ("Programm arbeitet mit Unicode und setzt Windows NT voraus!"), 
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

      hwnd = CreateWindow (szAppName,                 // Name der Fensterklasse
                  TEXT ("Das erste echte Programm"),  // Fenstertitel
                  WS_OVERLAPPEDWINDOW,                // Fensterstil
                  CW_USEDEFAULT,                      // X-Position des Fensters
                  CW_USEDEFAULT,                      // Y-Position des Fensters
                  CW_USEDEFAULT,                      // Fensterbreite
                  CW_USEDEFAULT,                      // Fensterhöhe
                  NULL,                               // übergeordnetes Fenster
                  NULL,                               // Menü
                  hInstance,                          // Programm-Kopiezähler (Programm-ID)
                  NULL) ;                             // zusätzliche Parameter

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;

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

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     HDC         hdc ;
	 static HWND hEdit;
	 static HWND hButton;
     PAINTSTRUCT ps ;
     RECT        rect ;
	 const char  szText[] = "Hallo, dies ist der Text.";
	 char static buffer[16];
	 const char pw[] = "Interkom";

     switch (message)
     {
     case WM_CREATE:
		 {

		 hEdit = CreateWindowEx(WS_EX_CLIENTEDGE,
                                   "edit",
                                   buffer,    // <- das ist der Inhalt der Editfelds
                                   WS_CHILD | WS_VISIBLE | WS_VSCROLL | ES_MULTILINE |
                                              ES_AUTOVSCROLL,
                                   0, 0, 0, 0,
                                   hwnd,
                                   NULL,
                                   ((LPCREATESTRUCT) lParam) -> hInstance,
                                   NULL);

		 hButton = CreateWindow("button","Login",
                                  WS_CHILD | WS_VISIBLE,
                                  0, 0, 0, 0,
                                  hwnd,
                                  NULL,
                                  ((LPCREATESTRUCT) lParam) -> hInstance,
                                  NULL);

		 }

          return 0 ;

	 case WM_SIZE:
		 MoveWindow(hEdit, 0, 0, 100, 20, TRUE);
		 MoveWindow(hButton, 0, 20, 100, 20, TRUE);
		 return 0;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;

          GetClientRect (hwnd, &rect) ;

          EndPaint (hwnd, &ps) ;

		  return 0 ;

	 case WM_COMMAND:
		 {
         if (lParam == (LPARAM)hButton)
         {
            if (HIWORD(wParam) == BN_CLICKED)
			{
				if(buffer==pw)
					MessageBeep(MB_OK);
			}
         }
		 }
         return 0;

     case WM_DESTROY:
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

Stichwort: strcmp.