how to write hello world in assembler under windows?

Question

Hi 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 help of c functions on windows?

thx

Answer 1

NASM examples.

; ----------------------------------------------------------------------------
; helloworld.asm
;
; This is a Win32 console program that writes "Hello, World" on one line and
; then exits.  It needs to be linked with a C library.
; ----------------------------------------------------------------------------

    global _main
    extern _printf

    section .text
_main:
    push message
    call _printf
    add  esp, 4
    ret
message:
    db 'Hello, World', 10, 0

Then run

nasm -fwin32 helloworld.asm
gcc helloworld.obj
a

There's also The Clueless Newbies Guide to Hello World in Nasm without the use of a C library. Then the code would look like this.

org 100h
mov dx,msg
mov ah,9
int 21h
mov ah,4Ch
int 21h
msg db 'Hello, World!',0Dh,0Ah,'$'

Good luck.

Answer 2

This example shows how to go directly to the Windows API and not link in the C Standard Library.

    global _main
    extern  _GetStdHandle@4
    extern  _WriteFile@20
    extern  _ExitProcess@4

    section .text
_main:
    ; DWORD  bytes;    
    mov     ebp, esp
    sub     esp, 4

    ; hStdOut = GetstdHandle( STD_OUTPUT_HANDLE)
    push    -11
    call    _GetStdHandle@4
    mov     ebx, eax    

    ; WriteFile( hstdOut, message, length(message), &bytes, 0);
    push    0
    lea     eax, [ebp-4]
    push    eax
    push    (message_end - message)
    push    message
    push    ebx
    call    _WriteFile@20

    ; ExitProcess(0)
    push    0
    call    _ExitProcess@4

    ; never here
    hlt
message:
    db      'Hello, World', 10
message_end:

To compile, you'll need NASM and LINK.EXE (from Visual studio Standard Edition)

   nasm -fwin32 hello.asm
   link /subsystem:console /nodefaultlib /entry:main hello.obj 

Answer 3

Unless you call some function this is not at all trivial. (And, seriously, there's no real difference in complexity between calling printf and calling a win32 api function.)

Even DOS int 21h is really just a function call, even if its a different API.

If you want to do it without help you need to talk to your video hardware directly, likely writing bitmaps of the letters of "Hello world" into a framebuffer. Even then the video card is doing the work of translating those memory values into VGA/DVI signals.

Note that, really, none of this stuff all the way down to the hardware is any more interesting in ASM than in C. A "hello world" program boils down to a function call. One nice thing about ASM is that you can use any ABI you want fairly easy; you just need to know what that ABI is.

Answer 4

Also check out Steve Gibson's Small Is Beautiful windows assembly starter kit.