Esempio di creazione di una semplice finestra vuota:

codice:
#define STRICT
#include <windows.h>

#define MAIN_WNDCLASS   "MiaClasseFinestra"

LRESULT CALLBACK Main_WndProc (HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
        case WM_CREATE:
            return 0;

        case WM_PAINT:
        {
            HDC hdc;
            PAINTSTRUCT ps;

            hdc = BeginPaint (hWnd, &ps);

            EndPaint (hWnd, &ps);
            return 0;
        }

        case WM_DESTROY:
            PostQuitMessage (0);
            return 0;

        case WM_CLOSE:
            DestroyWindow (hWnd);
            return 0;
    }

    return DefWindowProc (hWnd, uMsg, wParam, lParam);
}


INT APIENTRY WinMain (HINSTANCE hInstance, HINSTANCE hPrevious, LPSTR lpszCmdLine, INT iCmdShow)
{
    WNDCLASSEX  wcx;
    HWND        hWnd;
    MSG         msg;

    wcx.cbSize        = sizeof (wcx);
    wcx.style         = CS_HREDRAW | CS_VREDRAW;
    wcx.lpfnWndProc   = (WNDPROC) Main_WndProc;
    wcx.cbClsExtra    = 0;
    wcx.cbWndExtra    = 0;
    wcx.hInstance     = hInstance;
    wcx.hIcon         = NULL;
    wcx.hIconSm       = NULL;
    wcx.hCursor       = LoadCursor (NULL, IDC_ARROW);
    wcx.hbrBackground = (HBRUSH) (COLOR_WINDOW+1);
    wcx.lpszMenuName  = NULL;
    wcx.lpszClassName = MAIN_WNDCLASS;

    if (!RegisterClassEx (&wcx))
    {
        MessageBox (NULL, "Errore nella registrazione della classe",
                    "ERRORE", MB_OK | MB_ICONEXCLAMATION);
        return 1;
    }

    hWnd = CreateWindow (MAIN_WNDCLASS, "Titolo finestra", WS_OVERLAPPEDWINDOW,
                         CW_USEDEFAULT, 0, 300, 300,
                         NULL, NULL, hInstance, NULL);

    if (hWnd == NULL)
    {
        MessageBox (NULL, "Errore nella creazione della finestra",
                    "ERRORE", MB_OK | MB_ICONEXCLAMATION);
        return 1;
    }

    ShowWindow (hWnd, SW_SHOWNORMAL);
    UpdateWindow (hWnd);

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

    return 0;
}