How can I write a "Hello World" app in assembly language? [duplicate]

Question

Possible Duplicate:
how to write hello world in assembler under windows?

I've often heard of applications written using the language of the gods, assembly language. I've never tried though, and I don't even have a clue how to do it.

If I wanted to dabble, how would I go about doing it? I know absolutely nothing about what is required, although presumably some kind of compiler and Notepad.

Just purely out of curiousity, what would I need to write a "Hello World!" application?

Edit to add, I am running Windows 7 64bit

Edit to add, I wonder if there is an assembly language plugin for Visual Studio?

Answer 1

For this, you gain nothing by writing 64-bit code -- you might as well stick to 32-bit code.

If you want output to a MessageBox, it could look like this:

.386
.MODEL flat, stdcall

MessageBoxA PROTO near32 stdcall, window:dword, text:near32,
        windowtitle:near32, style:dword

.stack 8192

.data
message db "Hello World!", 0
windowtitle   db "Win32 Hello World.", 0

.code
main proc
        invoke MessageBoxA, 0, near32 ptr message, near32 ptr windowtitle, 0
        ret
main endp
        end main

If you want output to the console, it's (strangely enough) a bit more complex:

.386
.MODEL flat, stdcall

getstdout = -11

WriteFile PROTO NEAR32 stdcall,     \
        handle:dword,                   \
    buffer:ptr byte,        \
        bytes:dword,                    \
        written: ptr dword,             \
        overlapped: ptr byte

GetStdHandle PROTO NEAR32, device:dword

ExitProcess PROTO NEAR32, exitcode:dword

.stack 8192

.data
message db "Hello World!"
msg_size equ $ - offset message

.data?
written  dd ?

.code
main proc   
    invoke GetStdHandle, getstdout
    invoke WriteFile,                   \
           eax,                         \
           offset message,              \
           msg_size,                    \
           offset written,              \
           0

    invoke ExitProcess, 0
main endp
        end main

In theory, moving to 64 bit code doesn't make a lot of difference -- for example, you can use the same functions in both. In reality, it's a bit painful, because the calling convention for 64-bit code is somewhat complex, and you can't use MASM's invoke for 64-bit code. Working code wouldn't be a whole lot more complex, but getting the code working probably would be a bit more work. The general idea is that for 64-bit code, you allocate space on the stack for all your parameters, but the first N parameters that are small enough to fit, go in registers.

Answer 2

Have a look at WinAsm.