Learning ASM

[Cybrg641]

I have MASM32. It seems to be pretty good. Go to this site for compilers and tutorials. By the way, could you send me the code that you used to open/close your cd drive? Thanks.

Thank you very much

[Paul282]

Try this
http://www.programmingtutorials.com/

damn, I dont know why I didnt ever try that URL before



BTW Thanks!

[Edited by denniswrenn on 08-20-2000 at 08:48 PM]

http://burks.bton.ac.uk/burks/langua...m/artof001.htm

[Paul282]

Yeah, I've been through that one.

I tend to find that you're better of with a book when it comes to ASM. (not that I'm an experienced ASM programmer) I also find that books cover the topic in much more depth and that has been very important to me so far in learning ASM.

I got this book...

http://www.amazon.com/exec/obidos/AS...470099-9752032



[Edited by Paul282 on 08-21-2000 at 10:59 PM]

[Cybrg641]

$73.00?!?!?! Jeez!! That's way too much for me!

[Paul282]

I'm always happy to spend money on books. Net tutorials are good but if I buy a book I'm more inclined to sit down and actually learn the topic in depth.

Sort of like an investment in myself, the payback comes when I ask for twice as much in my next job :-)

It's worked well so far anyway, I'm not 30 yet, I didn't even finish school let alone go to college and I earn over US$100k a year in the IT industry!

I have a problem with modesty though

[V(ery) Basic]

It shines through like a supernova

[Paul282]

can't even blame alcohol for that comment!

[V(ery) Basic]

I'm posting this here, because it's such a petty question it isn't worthy of a new thread:

Could somebody post just a little source code (ASM), because I'm really interested to see what it look like.

Thyroid.

[parksie]

From the MASM32 website:

; ######################################################################### 

      .386 
      .model flat, stdcall 
      option casemap :none   ; case sensitive 

; ######################################################################### 

      include \masm32\include\windows.inc 
      include \masm32\include\user32.inc 
      include \masm32\include\kernel32.inc 

      includelib \masm32\lib\user32.lib 
      includelib \masm32\lib\kernel32.lib 

; ######################################################################### 

      ;============= 
      ; Local macros 
      ;============= 

      szText MACRO Name, Text:VARARG 
        LOCAL lbl 
          jmp lbl 
            Name db Text,0 
          lbl: 
        ENDM 

      m2m MACRO M1, M2 
        push M2 
        pop  M1 
      ENDM 

      return MACRO arg 
        mov eax, arg 
        ret 
      ENDM 

        ;================= 
        ; Local prototypes 
        ;================= 
        WinMain PROTO :DWORD,:DWORD,:DWORD,:DWORD 
        WndProc PROTO :DWORD,:DWORD,:DWORD,:DWORD 
        TopXY PROTO   :DWORD,:DWORD 

    .data 
        szDisplayName db "Template",0 
        CommandLine   dd 0 
        hWnd          dd 0 
        hInstance     dd 0 

    .code 

start: 
        invoke GetModuleHandle, NULL 
        mov hInstance, eax 

        invoke GetCommandLine 
        mov CommandLine, eax 

        invoke WinMain,hInstance,NULL,CommandLine,SW_SHOWDEFAULT 
        invoke ExitProcess,eax 

; ######################################################################### 

WinMain proc hInst     :DWORD, 
             hPrevInst :DWORD, 
             CmdLine   :DWORD, 
             CmdShow   :DWORD 

        ;==================== 
        ; Put LOCALs on stack 
        ;==================== 

        LOCAL wc   :WNDCLASSEX 
        LOCAL msg  :MSG 

        LOCAL Wwd  :DWORD 
        LOCAL Wht  :DWORD 
        LOCAL Wtx  :DWORD 
        LOCAL Wty  :DWORD 

        ;================================================== 
        ; Fill WNDCLASSEX structure with required variables 
        ;================================================== 

        mov wc.cbSize,         sizeof WNDCLASSEX 
        mov wc.style,          CS_HREDRAW or CS_VREDRAW \ 
                               or CS_BYTEALIGNWINDOW 
        mov wc.lpfnWndProc,    offset WndProc 
        mov wc.cbClsExtra,     NULL 
        mov wc.cbWndExtra,     NULL 
        m2m wc.hInstance,      hInst 
        mov wc.hbrBackground,  COLOR_BTNFACE+1 
        mov wc.lpszMenuName,   NULL 
        mov wc.lpszClassName,  offset szClassName 
          invoke LoadIcon,hInst,500    ; icon ID 
        mov wc.hIcon,          eax 
          invoke LoadCursor,NULL,IDC_ARROW 
        mov wc.hCursor,        eax 
        mov wc.hIconSm,        0 

        invoke RegisterClassEx, ADDR wc 

        ;================================ 
        ; Centre window at following size 
        ;================================ 

        mov Wwd, 500 
        mov Wht, 350 

        invoke GetSystemMetrics,SM_CXSCREEN 
        invoke TopXY,Wwd,eax 
        mov Wtx, eax 

        invoke GetSystemMetrics,SM_CYSCREEN 
        invoke TopXY,Wht,eax 
        mov Wty, eax 

        szText szClassName,"Template_Class" 

        invoke CreateWindowEx,WS_EX_OVERLAPPEDWINDOW, 
                              ADDR szClassName, 
                              ADDR szDisplayName, 
                              WS_OVERLAPPEDWINDOW, 
                              Wtx,Wty,Wwd,Wht, 
                              NULL,NULL, 
                              hInst,NULL 
        mov   hWnd,eax 

        invoke LoadMenu,hInst,600  ; menu ID 
        invoke SetMenu,hWnd,eax 

        invoke ShowWindow,hWnd,SW_SHOWNORMAL 
        invoke UpdateWindow,hWnd 

      ;=================================== 
      ; Loop until PostQuitMessage is sent 
      ;=================================== 

    StartLoop: 
      invoke GetMessage,ADDR msg,NULL,0,0 
      cmp eax, 0 
      je ExitLoop 
      invoke TranslateMessage, ADDR msg 
      invoke DispatchMessage,  ADDR msg 
      jmp StartLoop 
    ExitLoop: 

      return msg.wParam 

WinMain endp 

; ######################################################################### 

WndProc proc hWin   :DWORD, 
             uMsg   :DWORD, 
             wParam :DWORD, 
             lParam :DWORD 

    .if uMsg == WM_COMMAND 
    ;======== menu commands ======== 
        .if wParam == 1000 
            invoke SendMessage,hWin,WM_SYSCOMMAND,SC_CLOSE,NULL 
        .elseif wParam == 1900 
            szText TheMsg,"Assembler, Pure & Simple" 
            invoke MessageBox,hWin,ADDR TheMsg,ADDR szDisplayName,MB_OK 
        .endif 
    ;====== end menu commands ====== 

    .elseif uMsg == WM_CLOSE 
        szText TheText,"Please Confirm Exit" 
        invoke MessageBox,hWin,ADDR TheText,ADDR szDisplayName,MB_YESNO 
          .if eax == IDNO 
            return 0 
          .endif 
    .elseif uMsg == WM_DESTROY 
        invoke PostQuitMessage,NULL 
        return 0 
    .endif 

    invoke DefWindowProc,hWin,uMsg,wParam,lParam 

    ret 

WndProc endp 

; ######################################################################## 

TopXY proc wDim:DWORD, sDim:DWORD 

    shr sDim, 1      ; divide screen dimension by 2 
    shr wDim, 1      ; divide window dimension by 2 
    mov eax, wDim    ; copy window dimension into eax 
    sub sDim, eax    ; sub half win dimension from half screen dimension 

    return sDim 

TopXY endp 

; ######################################################################## 

end start

[V(ery) Basic]

Hmmm. It's not as harsh as I thought it would be.

Thanks, parksie.

[parksie]

Having started to learn this morning, I can confidently say that it is definitely not as hard as people say.

[V(ery) Basic]

Yeah, I was expecting something where you had to intercept all the mouse messaages and keyboard messages, and you had to create the window yourself and set the pixels yourself. It just seems like a primitive C++, though.

[parksie]

Not really. You do need to set up a window procedure and all that, but a basic program in C++ takes up about 25K, and that program I gave assembles into 5K, and uses NO DLLs WHATSOEVER. Also, when doing asm, you can optimise it by hand by method, because there are new, more efficient ways to do certain algorithms.

[Paul282]

bit of a reality check though. That's MASM32! which has quite a bit added to make it easier. to actually write your own code you'd need a better understanding of ASM in it's normal form.

Here's hello world

title Hello World Program         (hello.asm)

; This program displays "Hello, world!"

.model small
.stack 100h
.data
message db "Hello, world!",0dh,0ah,'$'

.code
main proc
    mov  ax,@data
    mov  ds,ax

    mov  ah,9
    mov  dx,offset message
    int  21h

    mov  ax,4C00h
    int  21h
main endp

end main

There is a lot to learn before you can really start. Don't get me wrong, what you learn about CPU's, registers and memory is valuable in any language. But you'd need to know basic ASM syntax before you used MASM32.

You should be able to look at the above code and see it is only using 16 bit registers.

Int 21h is a dos interrupt, but other than that you'd need understanding of the AX, DS and quite a few other register's functions. I've only been in this for a few months and have hardly written anything, but it's fascinating. The commands are one for one based on machine code!

[parksie]

Paul - thanks for that, I needed some example code to do this. Why is the string terminated with a '$' not '\0'?
Also, when you write your program, do you need to worry about the register state before or after your program runs?

[Darkwraith]

The string is terminated with a '$' because INT 21h function 09h stops displaying characters once a '$' is reached.

I really don't think you have to worry about register states before and after your application runs.