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confusion in asembly language
Posted: Thu Dec 06, 2007 12:21 am
by vishal
i am trying to display a string entered by the user but it is not giving any ouptut. plz help.
i dont know the code for the enter key so i have used '+' instead
i have made
Print : for displaying a string using int 10h
GET_CHAR : for netering a character
COM1 : for moving COMMAND (the string to be displayed) into si and to call Print
and finally the start:
Code: Select all
jmp start
Print:
lodsb
or al, al
jz PrintDone
mov ah, 0eh
int 10h
jmp Print
PrintDone:
ret
GET_CHAR:
MOV AH,00
INT 0x16 ;character is stored in AL register
RET
COM1 : ; this procedure moves COMMAND into si and displays it using Print
xor si,si
mov si,COMMAND
CALL Print
ret
start:
xor si,si
mov cx,0000H
LBL1 :
CALL GET_CHAR ;call get_char to enter a character
CMP AL,'+' ;i dont know the code for enter so written '+' instead
JE LBL2 ;if '+' has been entered the string is over
inc cx
mov BYTE[si],al ;else store the next character in COMMAND
call Print :to display the character entered
inc si
jmp LBL1
LBL2 :
mov BYTE[si],0 ;make last character 0
inc cl
sub si,cl
mov di,[COMMAND] ;copy the string from si to COMMAND
mov [di],si
call COM1
jmp $
COMMAND db 0
please point out any other errors if any....
Posted: Thu Dec 06, 2007 7:03 am
by ManOfSteel
Try making the buffer (COMMAND db 0) bigger as you will cause a buffer overflow when the command is more than one character long.
Print should work when used as in
COM1:, but probably won't work in
LBL1: since si points to address 0 (
xor si,si after
start:).
Try this instead:
Code: Select all
start:
mov si,COMMAND
...
inc cx
mov BYTE[si],al
mov ah,0eh
int 10h
inc si
jmp LBL1
...
(BTW,
xor si,si in
COM1: is useless).
Code: Select all
mov di,[COMMAND] ;copy the string from si to COMMAND
This will only copy the first byte of COMMAND into di.
Posted: Thu Dec 06, 2007 7:54 am
by Combuster
i dont know the code for the enter key so i have used '+' instead
(I thought we put up a link to this in a prominent location)
Posted: Thu Dec 06, 2007 10:02 am
by JAAman
you mean the ascii code for enter...? i thought everyone knew that!
btw, its 0x13...
Posted: Fri Dec 07, 2007 12:10 am
by vishal
i am sorry about that enter key code as i am so messed with program....
i want to write a program that stores the string entered by the user in a string variable and then display it with the help of the string variable
in the above code i store the string in COMMAND and later print it but am unable to do it ...
ManOfSteel thanks a lot for your help but iwas unable to do so by your modifications
Combuster,JAAman thank you for replies
plz somebdy help
Posted: Fri Dec 07, 2007 12:31 pm
by ManOfSteel
@JAAman:
You mean 13 (in decimal).
@vishal:
What I suggested in my last post is enough to make it work.
So what's the problem? What's happening? What does it display? Does it crash? Please, post the modified code.
You're writing it for DOS, right? You didn't forget the org 100h, did you?
Posted: Sun Dec 09, 2007 10:00 am
by JAAman
@JAAman:
You mean 13 (in decimal).
doh! i knew i was going to do that... mixing my decimal and hex
reply
Posted: Sat Dec 15, 2007 4:38 pm
by matias_beretta
here is the code you want:
Code: Select all
org 100h
mov si, String1
call print
mov di, String2
call input
mov si, String3
call print
mov si, String2
call print
mov si, String4
call print
mov ah, 0h
int 16h
ret
String1:
db "What is your name?", 13, 10, 0
String2:
rb 11
String3:
db 13, 10, "Your name is ", 0
String4:
db '.', 13, 10, 0
print:
mov ah, 0eh
.a:
mov al, [si]
inc si
cmp al, 0
je .b
int 10h
jmp .a
.b:
ret
input:
mov cx, 0
.a:
mov ah, 0h
int 16h
cmp al, 0dh
je .b
cmp cx, 10
je .a
mov [di], al
inc di
mov ah, 0eh
int 10h
inc cx
jmp .a
.b:
mov byte [di], 0
ret
Posted: Mon Dec 17, 2007 2:00 am
by os64dev
Might i point out that giving the 'solution' code does not help developers. It only helps them to get to the next problem faster without understanding what they are doing. If you want the help point to the faulting code and explain why it is wrong and let them come up with the solution.
Posted: Mon Dec 17, 2007 7:06 am
by ManOfSteel
os64dev, I can't agree more.
let them come up with the solution
I was waiting for that to happen. After posting enough suggestions and corrections, I waited for days but the OP never replied. Considering the oddly written and sometimes totally incomprehensible and useless code in the source and then the sudden loss of interest of the OP when I asked for the corrected code, I'm suspecting he wants to "program" without even knowing the very basics of assembler.