How to write hello world in assembler under Windows?

Question

I wanted to write something basic in assembly under Windows, I\'m using NASM, but I can\'t get anything working.

How to write and compile hello world without the he

Answer 1

To get an .exe with NASM'compiler and Visual Studio's linker this code works fine:

global WinMain
extern ExitProcess  ; external functions in system libraries 
extern MessageBoxA

section .data 
title:  db 'Win64', 0
msg:    db 'Hello world!', 0

section .text
WinMain:
    sub rsp, 28h  
    mov rcx, 0       ; hWnd = HWND_DESKTOP
    lea rdx,[msg]    ; LPCSTR lpText
    lea r8,[title]   ; LPCSTR lpCaption
    mov r9d, 0       ; uType = MB_OK
    call MessageBoxA
    add rsp, 28h  

    mov  ecx,eax
    call ExitProcess

    hlt     ; never here

If this code is saved on e.g. "test64.asm", then to compile:

nasm -f win64 test64.asm

Produces "test64.obj" Then to link from command prompt:

path_to_link\link.exe test64.obj /subsystem:windows /entry:WinMain  /libpath:path_to_libs /nodefaultlib kernel32.lib user32.lib /largeaddressaware:no

where path_to_link could be C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin or wherever is your link.exe program in your machine, path_to_libs could be C:\Program Files (x86)\Windows Kits\8.1\Lib\winv6.3\um\x64 or wherever are your libraries (in this case both kernel32.lib and user32.lib are on the same place, otherwise use one option for each path you need) and the /largeaddressaware:no option is necessary to avoid linker's complain about addresses to long (for user32.lib in this case). Also, as it is done here, if Visual's linker is invoked from command prompt, it is necessary to setup the environment previously (run once vcvarsall.bat and/or see MS C++ 2010 and mspdb100.dll).