ELS message loop

#include<Windows.h>
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPreInstance,LPSTR ipCmdLine,int nCmdShow)
{
    // Initialize window class .
    WNDCLASSEX  db;
    HWND hWnd;
    MSG msg;// Structural variable .

    db.cbClsExtra = 0;
    db.cbSize = sizeof(WNDCLASSEX);
    db.cbWndExtra = 0;
    db.hbrBackground = (HBRUSH)COLOR_WINDOW;
    db.hCursor = NULL;
    db.hIcon = NULL;
    db.hIconSm = NULL;
    db.hInstance = hInstance;
    db.lpfnWndProc = NULL;
    db.lpszClassName = "els";
    db.lpszMenuName = NULL;
    db.style = CS_HREDRAW | CS_VREDRAW;

    if(0==RegisterClassEx(&db));
    {
        int a = GetLastError();
        return 0;
    }
    // create a window .hWnd Window handle Failure to return NULL.
    hWnd=CreateWindowEx(WS_EX_TOPMOST,"els","elsfangkuai",WS_OVERLAPPEDWINDOW,100,100,100,100,NULL,NULL,hInstance,NULL);

    if (NULL == hWnd)// Window handle . Unique identification of the window .
    {
        return 0;
    }

    // Display window
    ShowWindow(hWnd, nCmdShow);
    
    
    // Message loop . queue .
    // Return value ： Failure to return NULL.
    // Parameters 1： Point to MSG Pointer to the message structure .
    // Parameters 2： Specify the handle of the window , Use to process the message of this window .NULL Represents all the information of the current real column .
    // Parameters 3,4： Set the range of messages to be processed ,0,0 All information .
    GetMessage(&msg, NULL, 0, 0)//NULL He Fei NULL The difference between .
    {
        // This function converts virtual key messages into character messages . Character messages are sent to the call ready message queue .
        // Return value ： If the message is converted , Returns a nonzero value .
        // Parameters ： Point to MSG Pointer to the message structure .
        TranslateMessage(&msg);// Translate the news .

        // This function distributes a message to the window program .
        // Return value ： The return value is the value returned by the window program . Although the meaning of the return value depends on the information being dispatched , But the return value is usually ignored .
        // Parameters ： Point to MSG Pointer to the message structure .
        DispatchMessage(&msg);// Distribution message . Standard message Command message Notification message Custom message .
    }
    

    return 0;
}