新人报道，顺便给出我的第一个问题，请大神们多多关照

下面是全部的代码：
有兴趣的朋友复制运行一下，看看结果。

#include <stdio.h>
#include <windows.h>

LRESULT CALLBACK WinSunPROC(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
        case WM_CHAR:                                        //字符事件
        {
            char szChar[20];
            sprintf(szChar, "char is %d", wParam);
            MessageBox(hwnd, szChar, "hh", 0);
        }break;
        case WM_NCLBUTTONDOWN:                               //鼠标左键按下事件
        {
            MessageBox(hwnd, "mouse clicked", "hh", 0);
            HDC hdc;
            hdc = GetDC(hwnd);
            TextOut(hdc, 0, 50, "鼠标左键", strlen("鼠标左键"));
            ReleaseDC(hwnd, hdc);
        }break;
        case WM_PAINT:                                      //窗口重绘事件
        {
            HDC hDc;
            PAINTSTRUCT ps;

            hDc = BeginPaint(hwnd, &ps);
            TextOut(hDc, 0, 0, "第一课", strlen("第一课"));
            EndPaint(hwnd, &ps);
        }break;
        case WM_CLOSE:                                    //窗口关闭事件                                 
        {
            if (IDYES == MessageBox(hwnd, "是否真的结束？", "hh", MB_YESNO))
            {
                DestroyWindow(hwnd);                     //销毁该窗口
            }
        }break;
        case WM_DESTROY:                                 //窗口销毁事件  
        {
          PostQuitMessage(0);                            //往本线程的消息队列中发送一个。。。
        }break;
        default:
            return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(
    HINSTANCE  hInstance,
    HINSTANCE  hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow
    )
{
    WNDCLASS wndcls;

    wndcls.cbClsExtra    = 0;
    wndcls.cbClsExtra    = 0;
    wndcls.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    wndcls.hCursor       = LoadCursor(NULL,IDC_CROSS);
    wndcls.hIcon         = LoadIcon(NULL,IDI_APPLICATION);
    wndcls.hInstance     = hInstance;
    wndcls.lpfnWndProc   = WinSunPROC;
    wndcls.lpszClassName = "xu";
    wndcls.lpszMenuName  = NULL;
    wndcls.style         = CS_HREDRAW | CS_VREDRAW;

    if (RegisterClass(&wndcls) == 0)
    {
        DWORD dw = GetLastError();    //87：参数无效
        MessageBox(NULL, TEXT("窗口类注册失败！"), TEXT("提示"), MB_OK);
        return 1;
    }

    HWND hwnd;
    hwnd = CreateWindow("xu", "测试", WS_OVERLAPPEDWINDOW, 10, 10, 600, 400, NULL, NULL, hInstance,NULL);

    if (hwnd)
    {
        ShowWindow(hwnd, SW_SHOWNORMAL);
    }
    else
    {
        DWORD dw = GetLastError();    //1407 :找不到窗口类别。
        MessageBox(NULL, TEXT("创建窗口失败！"), TEXT("提示"), MB_OK);
        UnregisterClass("xu", hInstance);  //移除注册
        return 1;
    }

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

刚开始学就找一个这么复杂的代码，太牛了。
我刚入门，还正在爬行呢。