ASM Community

Hello, im pretty new to ASM so im not really capable to fix my own code yet. Thats why im asking here, im hoping someone can tell me exactly what im doing wrong. So i can learn from your experience.
I can write the rwally basic program that displays a console window and where you can just type in it.

.MODEL SMALL
.CODE
MOV AH, 08H
INT 21H
MOV DL, AL
MOV AH, 02H
INT 21H
MOV AH, 4CH
INT 21H
END

Just to show you how 'far' i am. As you can see i just started out.
But i do know C++, so i thought im gonna write a simple app that just brings up the console window.
I wrote this small code.

#include <windows.h>

void main()
{
	char buf[4];
	buf[0] = 'c';
	buf[1] = 'm';
	buf[2] = 'd';
	buf[3] = '\0';

	WinExec(buf,SW_SHOW);

	exit(1);
}

In MSVC++ you can disassemble you own code, so i did that and i got this output.

push        ebp
mov         ebp,esp
sub         esp,44h
push        ebx
push        esi
push        edi
lea         edi,
mov         ecx,11h
mov         eax,0CCCCCCCCh
rep stos    dword ptr 

mov         byte ptr ,63h
mov         byte ptr ,6Dh
mov         byte ptr ,64h
mov         byte ptr ,0

mov         esi,esp
push        5
lea         eax,
push        eax
call        dword ptr [KERNEL32_NULL_THUNK_DATA (004241f8)]
cmp         esi,esp
call        __chkesp (00401070)

push        1
call        exit (00401a30)

Okay, im not that good yet so this doesnt make much sens for me yet. But i tried to compile this code with a MASM compiler. But i gave an error for everyline of code.
All i added was this line at the top:

.MODEL SMALL
.CODE

and under that the ASM code i got from the disassembler.

This is the error i got most:
error A2005: instruction or register not accepted in current CPU mode.

Can someone just tell me why im getting this errors, and why  it isnt possible to use that ASM code and all.
Thanks for any help.

I know the difference between the ASM snippet i posted and the c++ code.
But i was wondering why the disassembled ASM code doesnt work.
It uses WinExec to open the cmd window, atleast thats what suppose to be happening iwth the (disassembled) ASM part.
btw, thanks for the link, ill take a look at it later. Im also reading a book about the basics of ASM.

vivendi,

Here is your C program in Win32 style MASM just to give you a start. I would recommend you forget about DOS based MASM unless you really have a need to write DOS programs. Go through the tutorials QvasiModo mentioned, they are all about writing Win32 programs in MASM and they are good.

.386
.model flat,stdcall
option casemap:none

include c:\masm32\include\windows.inc
include c:\masm32\include\kernel32.inc
include c:\masm32\include\user32.inc
includelib c:\masm32\lib\kernel32.lib
includelib c:\masm32\lib\user32.lib

main PROTO

.DATA

    buf BYTE 4 dup(0)

.CODE

start:

    call main
    invoke ExitProcess, 0    ; exit is from the C run-time library, use
                             ; this Win32 API function instead. You can
                             ; use the C run-time library from MASM, but
                             ; this is simpler.
main PROC

    mov buf[0], 'c'
    mov buf[1], 'm'
    mov buf[2], 'd'
    mov buf[3], 0
    
    ; Call WinExec the manual way
    ;
    ;push SW_SHOW
    ;lea  eax, buf
    ;push eax
    ;call WinExec
    
    ; Or you can use invoke
    ;
    invoke WinExec, ADDR buf, SW_SHOW 
    
    ret
    
main ENDP

end start

...And:

WinExec is fine to use. It's only a wrapper on CreateProcess, and Microsoft is not likely to drop support for it in 32-bit platforms since a lot of apps would break.

Shoo,

My goal was to duplicate his C program in MASM so he could see how the same program is written in MASM.

I agree with you, it is better to use the comspec environment variable to get it's path. I guess I should have pointed that out in my example. Sheesh :roll: