assembly code on Windows 8 x64

Question

I'm new to hardware near programming with assembly code. So I read a book about it and found this sample code for the NASM assembler:

segment .text                               ;code segment
global main                                 ;must be declared for linker
main:                                       ;tell linker entry point
mov edx,len                                 ;message length
mov ecx,msg                                 ;message to write
mov ebx,1                                   ;file descriptor (stdout)
mov eax,4                                   ;system call number (sys_write)
int 0x80                                    ;call kernel
mov eax,1                                   ;system call number (sys_exit)
int 0x80                                    ;call kernel

segment .data                               ;data segment
msg db 'Hello, world!',0xa                  ;our dear string
len equ $ - msg                             ;length of our dear string

So I compiled it with the following commands:

nasm -f elf64 helloworld.asm
ld -s -o helloworld.exe helloworld.o

The assembler has no problem to assemble it and gives no errors, but the program crashes instantly. I read about different assembly-languages, but the point is that the assembly-code varies with different compilers not with different operating systems, so where is my mistake?

Answer 1

The code that you're showing is x86_32 linux code.
You can tell, because it uses int calls which Windows does not and this line:

nasm -f elf64 helloworld.asm

Produces output in ELF format, which is a linux executable.
Windows uses PE (portable executable) which is the MS EEE variant of COFF .

x64 code uses RAX , RBX ...., although the 32-bit variant registers EAX etc also feature heavily.

Before you can learn how to write assembly.
You need to know the ABI (calling conventions) and the API of a system.

For the ABI have a look at: Calling Conventions - PDF

If you want to know how to do API calls in Windows, write a simple C program that does the job and then get a disassembler and look at the x86 code.
For more info on the API calls have a look at MSDN, specifically:

Overview of x64 Calling Conventions
Windows Console functions
ExitProcess function

Answer 2

Assemble your executable on PE format and change the int 0x80 to a call ExecuteInterrupt128 . You can give it a same name. You can learn how to write a PE executable on NASM. Just go to the homepage of Stack Overflow.

The ExecuteInterrupt128 function must look like this:

push ebp
mov ebp, esp
cmp eax, byte +1
je SleepSystem
cmp eax, byte +4
je PrintString
...
SleepSystem:
push byte -1
call Sleep
leave
ret
PrintString:
push -11
call GetStdHandle
push byte +0
push byte +6
lea esi, [ebp-4]
push edx
push ecx
push eax
call WriteConsoleA
leave
ret

Or try this commands:

    nasm -f win32 -o executable.o executable.asm
    ld -o executable.exe executable.o