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Index > DOS > made my first Code [resolved]

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packet_50071



Joined: 31 Oct 2007
Posts: 15
packet_50071
this is my code
Code:
Ary db 123,145,143,146,0

lea ecx,[Ary]

startl:
mov eax,[ecx]
cmp eax,0
je quit
cmp ebx,eax
jle startl
mov ebx,eax
inc ecx
jmp startl

quit:
mov ax,4C00h
int 21h
    


I want to check if it works - i want it to show the highest value [which is in the ebx --- I hope]

Any help would be great Smile


Last edited by packet_50071 on 03 Nov 2007, 18:59; edited 1 time in total
Post 02 Nov 2007, 23:24
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bitRAKE



Joined: 21 Jul 2003
Posts: 2915
Location: [RSP+8*5]
bitRAKE
Some brief comments:
Code:
startl:
mov eax,[ecx]  ; Ary is bytes, but you load DWORD!
cmp eax,0
je quit
cmp ebx,eax      ; what is in EBX the first time?!
jle startl ; this will loop, but ECX hasn't been changed
mov ebx,eax
inc ecx                ; this should be in innerloop
jmp startl

quit:
mov ax,4C00h
int 21h    
This looks like DOS code - should be posted in the DOS section, imho.
Post 03 Nov 2007, 01:55
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packet_50071



Joined: 31 Oct 2007
Posts: 15
packet_50071
Code:
mov eax,[ecx]   ; Ary is bytes, but you load DWORD!     


How do I load the byte !

Should I repost this in DOS !
Post 03 Nov 2007, 16:06
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
use byte-sized register:
Code:
mov al, [ecx]
mov bh, [ecx]
    
Post 03 Nov 2007, 16:30
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bitRAKE



Joined: 21 Jul 2003
Posts: 2915
Location: [RSP+8*5]
bitRAKE
I used DEBUG from DOS when I first moved to Intel land. Hopefully, there are better debuggers in DOS, but I don't know what is availible in that regard. A good debugger will allow you to program in memory and test as you go - interactively. I piped instruction from a batch file to 'compile' my programs. Smile

Ollydbg works well for this in Windows.

In a debugger you will see a representation of internal machine state to better understand what is happening with each instruction. This is a good start.
Post 03 Nov 2007, 17:40
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packet_50071



Joined: 31 Oct 2007
Posts: 15
packet_50071
Thx for the help Smile

I will stick with fasm for now - when I move to Windows I will use Visual studio
its a good debugger for Windows Wink

My working code Smile


Code:
org 100h

mov ah,2
lea ecx,[Ary]
mov dl,0

startl:
mov al,[ecx]

cmp al,0
je quit

inc ecx

cmp al,dl
jle startl

mov dl,al
jmp startl

quit:
int 21h
mov ax,4C00h
int 21h

Ary db 109,108,102,0       
Post 03 Nov 2007, 18:50
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bitRAKE



Joined: 21 Jul 2003
Posts: 2915
Location: [RSP+8*5]
bitRAKE
Here are some DOS tools:
http://www.japheth.de/
Post 03 Nov 2007, 19:47
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Japheth



Joined: 26 Oct 2004
Posts: 151
Japheth
For such a simple program DEBUG is good enough:

http://www.japheth.de/Download/debug107.zip


David Lindauer has coded GRDB, which also has the nice and superior DEBUG interface + some goodies:

http://members.tripod.com/~ladsoft/grdb.htm


For those loving warm showers, there are fullscreen debuggers available as well:

http://www.bttr-software.de/products/insight/
http://www.programmersheaven.com/download/21643/download.aspx
Post 04 Nov 2007, 08:36
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