.386
.model flat ,stdcall

NULL equ 0
MB_OK equ 0

ExitProcess PROTO :DWORD
MessageBoxA PROTO :DWORD,:DWORD,:DWORD,:DWORD

includelib kernel32.lib
includelib user32.lib

.data
szText db "Hello, world!",0
szCaption db "Win32Asm",0

.code
start:
push MB_OK
lea eax,szCaption
push eax
lea eax,szText
push eax
push NULL
call messageboxa
xor eax,eax
push eax
call exitprocess
end start
都是按书上编写的怎么还报错,7.8.25.28有错,求解

还是不行了 提示:symbol not define和instruction or directive