x86 assembly

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02-06-2003
Shadow

x86 assembly

For a true first program, does this look ok?

Code:

; ------------------------ ; Message.asm ; ; This program will print ; 3 messages to the screen ; ------------------------ .MODEL SMALL .STACK .DATA MessageA db "This is a text message.", 13, 10, 13, 10, "$" MessageB db "This is another text message.", 13, 10, "$" MessageC db "This is yet another message.$" .CODE Main PROC Call Message1 Call Message2 Call Message3 Call Exit Message1 PROC mov dx, OFFSET MessageA mov ax, SEG MessageA mov ds, ax mov ah, 9 int 21h Message1 ENDP Message2 PROC mov dx, OFFSET MessageB mov ax, SEG MessageB mov ds, ax mov ah, 9 int 21h Message2 END Message3 PROC mov dx, OFFSET MessageC mov ax, SEG MessageC mov ds, ax mov ah, 9 int 21h Message3 END Exit PROC mov ax, 4c00h int 21h Exit ENDP Main ENDP END

I was messing around with functions and positioning text with this program.
Positioning text isn't as easy as it is in C.

I'm going to start expanding more upon files, input, and output soon.
02-06-2003
Carlos

It's ok, you could just optimize a little bit.
Instead of :

Code:

mov dx, OFFSET MessageA mov ax, SEG MessageA mov ds, ax

rather use

Code:

mov ax, @data mov ds, ax lea dx, ds:[MessageA]

ASM is cool! Have fun!
02-06-2003
Shadow

Thanks for the input Carlos. I did a little research on you, and you appear to know what you're talking about when it comes to ASM.

Thanks for the advice.
02-08-2003
Shadow

Apparently, because of the WhatKey.exe program I wrote in C programming for DOS which returns the scancode of the key you pressed, the enter/return key's scancode value is 13.

Is this what the number 13 means which is appended to the end of the DATA strings in my above example?
What does the number 10 mean? Is that some sort of a "stub" or "tag" or something to ensure that 13(return) gets executed?

I noticed that 13 doesn't work unless you also have 10.
02-16-2003
dizolve

DOS/Windows uses a combination of two characters to signify a new line...

ASCII #13 is CR - Carriage Return
ASCII #10 is LF - Line Feed
02-17-2003
Waldo2k2

What if he or I were coding for unix? Would unix choke on 10, or would it ignore it? I know that c/c++ compilers take \n and automatically put in \r\n if the target is Dos based. But since this is assembly, I was curious, I haven't toyed enought with it in the last year or so to remember.
02-17-2003
Shadow

> What if he or I were coding for unix?
I am using MS DOS 6.22 myself.
02-17-2003
Waldo2k2

Quote:

Originally posted by Shadow
> What if he or I were coding for unix?
I am using MS DOS 6.22 myself.

in my eyes there is no other dos :)
and that's ok if you didn't know about the unix thing, i was just curious.
02-17-2003
Shadow

> in my eyes there is no other dos :)
Yes. :)

> and that's ok if you didn't know about the unix thing, i was just curious.
Alrighty. Yeah, I haven't messed with the thing. Hopefully somebody else can help you.

Good luck.
02-18-2003
Carlos

If you're doing it in Assembly, you have to take care for OS compatibility yourself (e.g. you should forget "real" mode under Unix-es :) ).

Unless you call OS services, assembly language is quite the same in different OS-es.

Regarding the CR-LF (0Dh, 0Ah) pair - in Unix OS-es only LF (0Ah) is needed, this means newline.

CR might lead to unpredictable results - haven't tried yet, but probably it behaves differently, depending on the used editor.

Of course, there are different assemblers for different Unix versions (Linux, FreeBSD) - a quick search with google will provide you some really useful stuff.

If you're really interested, check this one: http://linuxassembly.org/

Have fun!