#include"windows.h"
#include"stdio.h"
#include"tchar.h"

LRESULT CALLBACK WndProc(
    HWND hwnd,
    UINT msg,
    WPARAM wparam,
    LPARAM lparam);


int WINAPI WinMain(
  HINSTANCE hInstance,
  HINSTANCE hPrevInstance,
  LPSTR lpCmdLine,
  int nShowCmd )
{
    BOOL msg_flag;
    MSG msg;
    HWND hwnd;
    WNDCLASS wndcls;

    wndcls.cbClsExtra=0;
    wndcls.cbWndExtra=0;
    wndcls.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
    wndcls.hCursor=LoadCursor(NULL,IDC_ARROW);
    wndcls.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    wndcls.hInstance=hInstance;
    wndcls.lpfnWndProc=WndProc;
    wndcls.lpszClassName=_T("C PROGRAM DESIGN");
    wndcls.lpszMenuName=NULL;
    wndcls.style=CS_HREDRAW|CS_VREDRAW;
    RegisterClass(&wndcls);
    hwnd=CreateWindow(_T("C PROGRAM DESIGN"),_T("HELLO 大家好!"),WS_OVERLAPPEDWINDOW,
         CW_USEDEFAULT,0, CW_USEDEFAULT,0,NULL,NULL,hInstance,NULL);
    ShowWindow(hwnd,SW_NORMAL);
    UpdateWindow(hwnd);
    msg_flag=GetMessage(&msg,hwnd,0,0);
    while(msg_flag)
    {
        if(msg_flag==-1)
            return -1;
        else
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }
}

LRESULT CALLBACK WndProc(
    HWND hwnd,
    UINT msg,
    WPARAM wparam,
    LPARAM lparam
)
{
    HDC hdc;
    PAINTSTRUCT ps;

    switch(msg)
    {
    case WM_CHAR:
        MessageBox(hwnd,TEXT("这是对话空"),_T("您好！"),0);
        break;
    case WM_LBUTTONDOWN:
        MessageBox(hwnd,TEXT("这是对话空"),_T("您好！"),0);
        hdc=GetDC(hwnd);
        TextOut(hdc,0,0,_T("这是程序员之家"),strlen("这是程序员之家"));
        ReleaseDC(hwnd,hdc);
        break;
    case WM_PAINT:
        HDC hdc;
        hdc=BeginPaint(hwnd,&ps);
        TextOut(hdc,0,0,_T("这是程序员之家"),strlen("这是程序员之家"));
        EndPaint(hwnd,&ps);
        ReleaseDC(hwnd,hdc);
        break;
    case WM_CLOSE:
        if(IDYES==MessageBox(hwnd,TEXT("是否真的结束？"),_T("message"),MB_YESNO))
            DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd,msg,wparam,lparam);
    return 0;
    }
}

我不知道你为什么会死循环，但我能解决：
这个窗体生成的代码本身就有一定问题。用DEV-C++自动生成的窗体代码来执行就不会死循环了。问题出在哪里看不出来，但先治标吧。
#include <windows.h>

/* This is where all the input to the window goes to */
LRESULT CALLBACK WndProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam) {
    HDC hdc;
    PAINTSTRUCT ps;

    switch(Message)
    {
    case WM_CHAR:
        MessageBox(hwnd,TEXT("这是对话空"),TEXT("您好！"),0);
        break;
    case WM_LBUTTONDOWN:
        MessageBox(hwnd,TEXT("这是对话空"),TEXT("您好！"),0);
        hdc=GetDC(hwnd);
        TextOut(hdc,0,0,TEXT("这是程序员之家"),strlen("这是程序员之家"));
        ReleaseDC(hwnd,hdc);
        break;
    case WM_PAINT:
        HDC hdc;
        hdc=BeginPaint(hwnd,&ps);
        TextOut(hdc,0,0,TEXT("这是程序员之家"),strlen("这是程序员之家"));
        EndPaint(hwnd,&ps);
        ReleaseDC(hwnd,hdc);
        break;
    case WM_CLOSE:
        if(IDYES==MessageBox(hwnd,TEXT("是否真的结束？"),TEXT("message"),MB_YESNO))
            DestroyWindow(hwnd);
        break;    case WM_DESTROY: {
            PostQuitMessage(0);
            break;
        }
        
        /* All other messages (a lot of them) are processed using default procedures */
        default:
            return DefWindowProc(hwnd, Message, wParam, lParam);
    }
    return 0;
}

/* The 'main' function of Win32 GUI programs: this is where execution starts */
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    WNDCLASSEX wc; /* A properties struct of our window */
    HWND hwnd; /* A 'HANDLE', hence the H, or a pointer to our window */
    MSG Msg; /* A temporary location for all messages */

    /* zero out the struct and set the stuff we want to modify */
    memset(&wc,0,sizeof(wc));
    wc.cbSize         = sizeof(WNDCLASSEX);
    wc.lpfnWndProc     = WndProc; /* This is where we will send messages to */
    wc.hInstance     = hInstance;
    wc.hCursor         = LoadCursor(NULL, IDC_ARROW);
   
    /* White, COLOR_WINDOW is just a #define for a system color, try Ctrl+Clicking it */
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszClassName = "WindowClass";
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION); /* Load a standard icon */
    wc.hIconSm         = LoadIcon(NULL, IDI_APPLICATION); /* use the name "A" to use the project icon */

    if(!RegisterClassEx(&wc)) {
        MessageBox(NULL, "Window Registration Failed!","Error!",MB_ICONEXCLAMATION|MB_OK);
        return 0;
    }

    hwnd = CreateWindowEx(WS_EX_CLIENTEDGE,"WindowClass","HELLO 大家好!",WS_VISIBLE|WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, /* x */
        CW_USEDEFAULT, /* y */
        640, /* width */
        480, /* height */
        NULL,NULL,hInstance,NULL);

    if(hwnd == NULL) {
        MessageBox(NULL, "Window Creation Failed!","Error!",MB_ICONEXCLAMATION|MB_OK);
        return 0;
    }

    /*
        This is the heart of our program where all input is processed and
        sent to WndProc. Note that GetMessage blocks code flow until it receives something, so
        this loop will not produce unreasonably high CPU usage
    */
    while(GetMessage(&Msg, NULL, 0, 0) > 0) { /* If no error is received... */
        TranslateMessage(&Msg); /* Translate key codes to chars if present */
        DispatchMessage(&Msg); /* Send it to WndProc */
    }
    return Msg.wParam;
}

这个得研究研究

谢谢你，我知道为什么进去死循环了，在消息循环中，msgflag只能得到一次消息，在while里msgflag得知一直不变，说已经入死循环，已经改过来了，还是要谢谢你

学习了。共勉