Asm window application skeleton

.386
.model flat,stdcall
option   casemap:none
    include \masm32\INCLUDE\windows.INC
        include \masm32\include\gdi32.inc
        include \masm32\include\user32.inc
        include \masm32\include\kernel32.inc
    include \masm32\INCLUDE\advapi32.INC

        includelib \masm32\lib\gdi32.lib
        includelib \masm32\lib\user32.lib
    includelib \masm32\lib\kernel32.lib
    includelib \masm32\lib\advapi32.lib
    includelib \masm32\lib\comctl32.lib

.DATA
    hinst DWORD 0
    hwnd DWORD 0

    WindowClass db "Window", 0
    WindowName db "Caption", 0

    MSG_Handle MSG <0>
.CODE
START:
    invoke GetModuleHandle, 0
    mov hinst, eax
    call Reg_Win_Class
    test eax,eax
    jz EXIT

    invoke CreateWindowEx, 0, addr WindowClass, addr WindowName, \
        WS_VISIBLE + WS_SYSMENU, 640, 480, 640, 480, 0, 0, hinst, 0

    mov hwnd, eax

    invoke ShowWindow, hwnd, 1
    invoke UpdateWindow, hwnd

Msg_Loop:

    invoke GetMessage, addr MSG_Handle, 0, 0, 0
    test eax,eax
    jz EXIT

    invoke TranslateMessage, addr MSG_Handle
    invoke DispatchMessage, addr MSG_Handle

    jmp Msg_Loop
EXIT:
    invoke  ExitProcess, 0

Reg_Win_Class proc
    local _WndClassStruct : WNDCLASS

    mov _WndClassStruct.style, 0
    mov _WndClassStruct.lpfnWndProc, WinProc
        mov _WndClassStruct.cbClsExtra, 0
        mov _WndClassStruct.cbWndExtra, 0
    push hinst
    pop _WndClassStruct.hInstance
    mov _WndClassStruct.lpszMenuName, 0
    mov _WndClassStruct.lpszClassName, offset WindowClass

    invoke LoadIcon, 0, 0
    mov _WndClassStruct.hIcon, eax

    invoke LoadCursor, 0, IDC_ARROW
    mov _WndClassStruct.hCursor, eax

    invoke CreateSolidBrush, 0ffffffh
    mov _WndClassStruct.hbrBackground, eax

    invoke RegisterClassA, addr _WndClassStruct
ret
Reg_Win_Class endp

WinProc proc \
        uses ebx esi edi hWnd :DWORD, MESS :DWORD, wParam :DWORD, lParam :DWORD

    cmp MESS, WM_DESTROY
    je  DESTROY_WIN

    invoke DefWindowProc, hWnd, MESS, wParam, lParam
    jmp ENDPROCEDURE

DESTROY_WIN:
    invoke PostQuitMessage, 0

ENDPROCEDURE:
ret 16
WinProc endp
END  START