Sorry for giving all the code, but the circumstances make me do so.
.model small
.stack 100h
;------------------------------------------------------------------------------------------
.data
messt db 'The string itself: $'
mesreal db 'The real length of string: $'
mesw db 'Enter the string: $'
mesp db 'Enter the position frome where to copy: $'
mesl db 'Enter the length of the string to copy: $'
mesend db 'The copied string: $'
pos db ? ; position from where to copy
len db ? ; length of substring
maxlen equ 20 ; max length of string
actlen equ ? ; real length of string
buffer db maxlen , actlen , maxlen dup (' ') ; string
string db maxlen dup ('0') ; where to copy
cur db ? ; cursor pos
;---------------------------------------------------------------------------------------------
.code
start:
mov ax,@data
mov ds,ax
;--------INPUT INVITATION----------------------------------
mov ah, 03h
int 10h
mov cur, dh
add cur, 1
mov dh, cur ; cursor
mov ah, 2
int 10h
lea dx, mesw ; invitation to input
mov ah, 9
int 21h
;----------------------------------------------------------
;-----------STRING INPUT-----------------------------------
lea dx, buffer
mov ah, 0ah
int 21h
;----------------------------------------------------------
;-------ACTUAL LENGTH OUTPUT----------------------------------
add cur, 1
mov dh, cur ; cursor
mov dl, 0
mov ah,2
int 10h
mov ah, 9
lea dx, mesreal
int 21h
mov ax, word ptr buffer[1]
mov ah,0
call printw
;------------------------------------------------------------
;-----------STRING OUTPUT----------------------------------
add cur, 1
mov dh, cur ; cursor
mov dl, 0
mov ah,2
int 10h
mov dx, offset messt
mov ah, 9
int 21h
xor bx,bx
mov bl, buffer[1]
mov buffer[bx+2], '$'
mov dx, offset buffer + 2
mov ah, 9
int 21h
;-----------------------------------------------------------
;--------GETTING THE POS & LENGTH----------------------------
; position ----
add cur, 1
mov dh, cur ; cursor
mov dl, 0
mov ah, 2
int 10h
mov ah, 9
lea dx, mesp
int 21h
mov ah, 1
int 21h
mov pos, al
sub pos, 30h ; converting to number
; length ------
add cur, 1
mov dh, cur ; cursor
mov dl, 0
mov ah, 2
int 10h
mov ah, 9
lea dx, mesl
int 21h
mov ah, 1
int 21h
mov len, al
sub len, 30h ; converting to number
;----------COPYING--------------------------------------------
add cur, 1
mov dh, cur ; cursor
mov dl, 0
mov ah, 2
int 10h
mov ah, 9
lea dx, mesend
int 21h
call copy
mov ah, 9
lea dx, string
int 21h
;--------------------------
;-------------------------------------------------------------
mov ax, 4c00h ; exit to operating system.
int 21h
;---------COPY PROC------------------------------------
copy proc
cld
mov cx, word ptr len
mov ch, 0
mov bx, word ptr pos
mov bh, 0
lea si,buffer
mov ax, word ptr pos
mov ah, 0
inc ax
add si,ax
lea di, string
rep movsb
;-------ENDING----
mov bx, word ptr len
mov bh, 0
mov string[bx], '$'
ret
copy endp
;-------------------------------------------------------
;---OUTPUT IN ASCI---------------
printw proc
PUSH AX
PUSH CX
PUSH DX
PUSH BX
PUSH SP
PUSH BP
PUSH SI
PUSH DI
mov cx,0
mov bx,10
out_dec1:
mov dx,0
div bx
push dx
inc cx
cmp ax,0
jne out_dec1
dmet1:
pop dx
add dl,30h
mov ah,2h
int 21h
loop dmet1
pop di
pop si
pop bp
pop sp
pop bx
pop dx
pop cx
pop ax
ret
printw endp
;--------------------------------
end start ;
The problem is that while entering the loop rep movsb, program does nothing with the strings, no action. I see that by watching the variables.
This fact is quite dissapointing me because while writing the program, that procedure worked, at least, it did something with the strings. I created a blank program, and the procedure worked there also. I really see no reason why that's so. Maybe vecause of some flags, or what? I can rewrite it without rep movsb easily, but that's not needed.
Thanks for any help.
;---------COPY PROC------------------------------------
copy proc
cld
mov cx, word ptr len
mov ch, 0
mov bx, word ptr pos
mov bh, 0
lea si,buffer
mov ax, word ptr pos
mov ah, 0
inc ax
add si,ax
lea di, string
rep movsb
;-------ENDING----
mov bx, word ptr len
mov bh, 0
mov string[bx], '$'
ret
copy endp
;-------------------------------------------------------
Quang,
Welcome to the forum, do not be surprised when a Moderator moves this post to the 16bit programming area. It is where you will actually get better support but I will try to help you.
The following is causing your problem...
mov bx, word ptr pos
mov bh, 0
Setting bh to zero effectively trashes the pointer you were trying to put in BX
Same thing is going on here...
mov ax, word ptr pos
mov ah, 0
and here...
mov cx, word ptr len
mov ch, 0
Quang, you need to go over the entire program, these errors are everywhere.
hth,
Paul
I wish it caused the problems, but it's not. I use only the value in AL, so i set zero in AH.
As the matter of fact, the strings stay untouched, whether I do it or not :(
Those things cause nothing. I rewrited the algorithm, using lodsb instead of rep movsb. And it's working.
But why using rep movsb the strings are not executed, I don't know...
For the movs_ instructions the starting source address is DS:SI and the starting destination address is ES:DI.
lea si,buffer ; HERE'S THE SOURCE
mov ax, word ptr pos
mov ah, 0
inc ax
add si,ax
lea di, string ; HERE'S THE DESTINATION
I wanna say once more that this procedure works in a blank program perfectly.
I have no idea why it is working in your blank program. The program you posted is an EXE so the loader is setting DS and ES to the segment address of the PSP. Your code is setting DS to your data segment, but leaving ES set to the PSP, so the destination is in the PSP instead of in your data. When you set SI and DI you set only the offset addresses of the source and destination. Try adding a:
push ds
pop es
at the start of your procedure.
Had no idea that the problem lies beneath, cos' I read a lot about rep movsb and there wasn't written anywhere about it.
Thanks for knowlege, I owe u much :) Thanks again.