This post shows how to write a Win32 “Hello World” program in x86 assembly language using FASM – the flat assembler.
It is a direct translation of the C language Win32 “Hello World” program that can be found on the MSDN website:
http://msdn.microsoft.com/en-us/library/vstudio/bb384843.aspx
The following steps are required to create and display a basic window:
(1) Fill a WNDCLASSEX structure with information about the window. (2) Call RegisterClassEx to register the windows class. (3) Call CreateWindowEx to create the window. (4) Call ShowWindow and UpdateWindow to show the window. (5) Create a callback function (WndProc) to process any messages received by the application. (6) Create a main message loop that will dispatch the messages to the WndProc function. (7) Inside WndProc, handle the WM_PAINT message to print the "Hello World" greeting. |
Related Post
FASM – A Simple Win32 Text Editor
The FASM Code
To grab this code, select with the mouse and then copy and paste directly into the FASM IDE.
; -------------------------------------------------------------------------------------
; FASM version of Win32 Hello World:
; http://msdn.microsoft.com/en-us/library/vstudio/bb384843.aspx
; -------------------------------------------------------------------------------------
format PE GUI 4.0
entry win_main
include 'win32a.inc'
; -------------------------------------------------------------------------------------
section '.code' code readable executable
win_main:
; initialise the members of the wcex structure
; --------------------------------------------
; WNDCLASSEX
; UINT cbSize
; UINT style
; WNDPROC lpfnWndProc
; int cbClsExtra
; int cbWndExtra
; HINSTANCE hInstance
; HICON hIcon
; HCURSOR hCursor
; HBRUSH hbrBackground
; LPCTSTR lpszMenuName
; LPCTSTR lpszClassName
; HICON hIconSm
; --------------------------------------------
; the instance handle
invoke GetModuleHandle,0
mov [wcex.hInstance],eax
; cbSize
mov eax,sizeof.WNDCLASSEX
mov [wcex.cbSize],eax
; the windows proc
mov [wcex.lpfnWndProc],WndProc
; the windows style
mov [wcex.style],CS_HREDRAW+CS_VREDRAW
; load the icons
invoke LoadIcon,[wcex.hInstance],IDI_APPLICATION
mov [wcex.hIcon],eax
mov [wcex.hIconSm],eax
; load the cursor
invoke LoadCursor,NULL,IDC_ARROW
mov [wcex.hCursor],eax
; the brush for the background
mov [wcex.hbrBackground],COLOR_WINDOW+1
; the windows class name
mov dword [wcex.lpszClassName],szClass
; set to NULL
mov [wcex.cbClsExtra],0
mov [wcex.cbWndExtra],0
mov dword [wcex.lpszMenuName],NULL
; register wcex
; RegisterClassEx(&wcex)
invoke RegisterClassEx,wcex
test eax,eax
jz reg_error
; create the window
invoke CreateWindowEx,0,szClass,szTitle,WS_OVERLAPPEDWINDOW,\
CW_USEDEFAULT,CW_USEDEFAULT,\
500,100,NULL,NULL,[wcex.hInstance],NULL
test eax,eax
jz cr_error
mov [h_wnd],eax
; show and update the window
; ShowWindow(hWnd,SW_SHOWNORMAL)
invoke ShowWindow,[h_wnd],SW_SHOWNORMAL
; UpdateWindow(hWnd)
invoke UpdateWindow,[h_wnd]
msg_loop:
; the main message loop
; GetMessage(&msg,NULL,0,0)
invoke GetMessage,msg,NULL,0,0
cmp eax,1
jb exit
jne msg_loop
; TranslateMessage(&msg)
invoke TranslateMessage,msg
; DispatchMessage(&msg)
invoke DispatchMessage,msg
jmp msg_loop
reg_error:
invoke MessageBox,NULL,szRegError,szTitle,MB_ICONERROR+MB_OK
jmp exit
cr_error:
invoke MessageBox,NULL,szCreateError,szTitle,MB_ICONERROR+MB_OK
exit:
; return msg.wParam
invoke ExitProcess,[msg.wParam]
; -------------------------------------------------------------------------------------
proc WndProc uses ebx esi edi,hwnd,wmsg,wparam,lparam
; WndProc(hwnd,wmsg,wparam,lparam)
; callback function to process messages for the main window
cmp [wmsg],WM_PAINT
je .PAINT
cmp [wmsg],WM_DESTROY
je .DESTROY
.DEFAULT:
; DefWindowProc(hWnd,message,wParam,lParam)
invoke DefWindowProc,[hwnd],[wmsg],[wparam],[lparam]
jmp .DONE
.PAINT:
; hdc = BeginPaint(hWnd,&ps)
invoke BeginPaint,[hwnd],ps
mov [hdc],eax
; TextOut(hdc,5,5,greeting,len(greeting))
invoke TextOut,[hdc],5,5,szGreeting,12
; EndPaint(hWnd,&ps)
invoke EndPaint,[hwnd],ps
jmp .DONE
.DESTROY:
; PostQuitMessage(0)
invoke PostQuitMessage,0
xor eax,eax
.DONE:
ret
endp
; -------------------------------------------------------------------------------------
section '.idata' import data readable writeable
library kernel,'KERNEL32.DLL',\
user,'USER32.DLL',\
gdi,'GDI32.DLL'
import kernel,\
GetModuleHandle,'GetModuleHandleA',\
ExitProcess,'ExitProcess'
import user,\
RegisterClassEx,'RegisterClassExA',\
CreateWindowEx,'CreateWindowExA',\
ShowWindow,'ShowWindow',\
UpdateWindow,'UpdateWindow',\
GetMessage,'GetMessageA',\
TranslateMessage,'TranslateMessage',\
DispatchMessage,'DispatchMessageA',\
MessageBox,'MessageBoxA',\
DefWindowProc,'DefWindowProcA',\
BeginPaint,'BeginPaint',\
EndPaint,'EndPaint',\
PostQuitMessage,'PostQuitMessage',\
LoadIcon,'LoadIconA',\
LoadCursor,'LoadCursorA'
import gdi,\
TextOut,'TextOutA'
; -------------------------------------------------------------------------------------
section '.data' readable writeable
szClass TCHAR "Win32app",0
szTitle TCHAR "Win32 Application",0
szGreeting TCHAR "Hello World!",0
szRegError TCHAR "Call to RegisterClassEx failed!",0
szCreateError TCHAR "Call to CreateWindowEx failed!",0
wcex WNDCLASSEX
ps PAINTSTRUCT
msg MSG
h_wnd dd 0
hdc dd 0
; -------------------------------------------------------------------------------------
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Assembly Language Programming 