Programming Forums > Application Development > Assembly

teencoder · May 28th, 2007, 1:40 AM

Okay I'm done with school for a while and I decided to toy with systems programming after a crash course in assembly I decided to try something. The program boots but doesn't execute properly. I've examined my code but I haven't found any problem. So if you could help me I'd really appreciate. It was assembled in NASM.

(Toggle Plain Text)

[BITS 16]
ORG 0
mov AH,0x0
mov AL,0x0
int 0x10; enter 40x25 B/W text video mode
continue:
int 0x16;read key strokes
cmp AH,0x1C0D;test for an enter key stroke
je exit
mov AL,AH
int 10;display character
jmp continue
exit:
mov AH,0x0
int 19;warm boot
times 510-($-$$) db 0x0;fill up empty bytes
dw 0xAA55;make bootable

The program boots initializes the video mode but on a key press does nothing after a few key strokes it starts beeping with the keystrokes. The enter key does not trigger a warm boot. Any suggestions would be appreciated

grimpirate · May 28th, 2007, 4:26 PM

I'll refer you to the following posts I started here where I had similar inquiries and problems and also to a tutorial I posted on another forum:

Hope that helps ya, also I like to use the FASM compiler but that's a personal preference, however, their forum has lots of info
http://flatassembler.net/

teencoder · May 29th, 2007, 1:28 AM

Thanks I tried to fix a few things but it's still broke and I have no clue where. Guess this is what I get for diving in headfirst if anyone could take a look I'd appreciate it.

(Toggle Plain Text)

[BITS 16]
ORG 0
jmp initiate
nop
times 59 db 0xFF
initiate:
mov AH,0x0
mov AL,0x0
int 0x10;set video
jmp main
main:
continue:
int 0x16;read keyboard 
cmp AH,0x5A; test for enter key 
je end; close 
mov AL,AH
mov AH,0x0E
mov BH,1
int 10;display character 
mov AH,0
jmp continue; 
end:
jmp terminate
terminate:
mov AH,0x0;
int 19;
times 510-($-$$) db 0x0
dw 0xAA55;make bootable

grimpirate · May 29th, 2007, 11:44 AM

Where exactly does the program fail? Does it not accept the enter key at all? I suggest before trying to accept input, trying to output something beforehand. Also, some of your labels and instructions like jmp main and main: are unecessary, as is the jmp terminate with the terminate: label right after.
Also check out this post at the flatassembler page
http://board.flatassembler.net/topic.php?t=6088
That program prints Hello World! waits for a key press and when a key is entered it powers down, which I think is sort of what you're trying to achieve.

DaWei · May 29th, 2007, 12:40 PM

(Toggle Plain Text)

end:
jmp terminate
terminate:

Look at this and apply a little thought. Execution normally proceeds to the next instruction. A branch or call modifies that. Jumping to the next instruction is just a waste (as mentioned in Grim's post).

Now suppose you remove the worthless jump. The end and terminate labels now represent the same address. That doesn't consume any code or take any time, but what the hell good is it, except for introducing confusion?

I don't care how many trees you kill. Use a pencil and paper to solidify your thoughts. Trace lines from here to there. Disentangle spaghetti. Better to kill a tree than an innocent person when your critical code goes south.

May 28th, 2007, 1:40 AM	#1
teencoder Hobbyist Programmer Join Date: Jul 2005 Posts: 158 Rep Power: 0	Help with simple program Okay I'm done with school for a while and I decided to toy with systems programming after a crash course in assembly I decided to try something. The program boots but doesn't execute properly. I've examined my code but I haven't found any problem. So if you could help me I'd really appreciate. It was assembled in NASM. (Toggle Plain Text) [BITS 16] ORG 0 mov AH,0x0 mov AL,0x0 int 0x10; enter 40x25 B/W text video mode continue: int 0x16;read key strokes cmp AH,0x1C0D;test for an enter key stroke je exit mov AL,AH int 10;display character jmp continue exit: mov AH,0x0 int 19;warm boot times 510-($-$$) db 0x0;fill up empty bytes dw 0xAA55;make bootable [BITS 16] ORG 0 mov AH,0x0 mov AL,0x0 int 0x10; enter 40x25 B/W text video mode continue: int 0x16;read key strokes cmp AH,0x1C0D;test for an enter key stroke je exit mov AL,AH int 10;display character jmp continue exit: mov AH,0x0 int 19;warm boot times 510-($-$$) db 0x0;fill up empty bytes dw 0xAA55;make bootable The program boots initializes the video mode but on a key press does nothing after a few key strokes it starts beeping with the keystrokes. The enter key does not trigger a warm boot. Any suggestions would be appreciated __________________ Geeks may not be cool now but in the long run they prosper.

May 28th, 2007, 4:26 PM	#2
grimpirate King of Portal Join Date: Sep 2005 Posts: 420 Rep Power: 4	I'll refer you to the following posts I started here where I had similar inquiries and problems and also to a tutorial I posted on another forum: http://www.programmingforums.org/for...this-work.html http://www.programmingforums.org/for...l-in-fasm.html http://www.programmingforums.org/for...-question.html http://www.dreamincode.net/forums/showtopic20863.htm Hope that helps ya, also I like to use the FASM compiler but that's a personal preference, however, their forum has lots of info http://flatassembler.net/ __________________ Lo, there do I see my father. 'Lo, there do I see My mother, and my sisters, and my brothers. 'Lo, there do I see The line of my people... Back to the beginning. 'Lo, they do call to me. They bid me take my place among them. In the halls of Valhalla... Where the brave... May live... ...forever.. GrimBB \| Mimesis

May 29th, 2007, 1:28 AM	#3
teencoder Hobbyist Programmer Join Date: Jul 2005 Posts: 158 Rep Power: 0	Thanks I tried to fix a few things but it's still broke and I have no clue where. Guess this is what I get for diving in headfirst if anyone could take a look I'd appreciate it. (Toggle Plain Text) [BITS 16] ORG 0 jmp initiate nop times 59 db 0xFF initiate: mov AH,0x0 mov AL,0x0 int 0x10;set video jmp main main: continue: int 0x16;read keyboard cmp AH,0x5A; test for enter key je end; close mov AL,AH mov AH,0x0E mov BH,1 int 10;display character mov AH,0 jmp continue; end: jmp terminate terminate: mov AH,0x0; int 19; times 510-($-$$) db 0x0 dw 0xAA55;make bootable [BITS 16] ORG 0 jmp initiate nop times 59 db 0xFF initiate: mov AH,0x0 mov AL,0x0 int 0x10;set video jmp main main: continue: int 0x16;read keyboard cmp AH,0x5A; test for enter key je end; close mov AL,AH mov AH,0x0E mov BH,1 int 10;display character mov AH,0 jmp continue; end: jmp terminate terminate: mov AH,0x0; int 19; times 510-($-$$) db 0x0 dw 0xAA55;make bootable __________________ Geeks may not be cool now but in the long run they prosper. Last edited by teencoder; May 29th, 2007 at 1:29 AM. Reason: typos

May 29th, 2007, 11:44 AM	#4
grimpirate King of Portal Join Date: Sep 2005 Posts: 420 Rep Power: 4	Where exactly does the program fail? Does it not accept the enter key at all? I suggest before trying to accept input, trying to output something beforehand. Also, some of your labels and instructions like jmp main and main: are unecessary, as is the jmp terminate with the terminate: label right after. Also check out this post at the flatassembler page http://board.flatassembler.net/topic.php?t=6088 That program prints Hello World! waits for a key press and when a key is entered it powers down, which I think is sort of what you're trying to achieve. __________________ Lo, there do I see my father. 'Lo, there do I see My mother, and my sisters, and my brothers. 'Lo, there do I see The line of my people... Back to the beginning. 'Lo, they do call to me. They bid me take my place among them. In the halls of Valhalla... Where the brave... May live... ...forever.. GrimBB \| Mimesis

May 29th, 2007, 12:40 PM	#5
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	(Toggle Plain Text) end: jmp terminate terminate: end: jmp terminate terminate: Look at this and apply a little thought. Execution normally proceeds to the next instruction. A branch or call modifies that. Jumping to the next instruction is just a waste (as mentioned in Grim's post). Now suppose you remove the worthless jump. The end and terminate labels now represent the same address. That doesn't consume any code or take any time, but what the hell good is it, except for introducing confusion? I don't care how many trees you kill. Use a pencil and paper to solidify your thoughts. Trace lines from here to there. Disentangle spaghetti. Better to kill a tree than an innocent person when your critical code goes south. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Application Development > Assembly

Help with simple program