3 replies to this topic

[assembler_wanna_be]

There are many examples for reversing a string in assembler on the net but I couldn't find any which only one string is used. So I decided to write myself one. And below is what I've created. The only problem is that it doesn't work. It reverses a part of the string a adds some characters at its end. Why is that? I've tried turbo debugging it but I cannot understand where actually string1 is visualised. Thank you in advance!

.model small

.data

	string1	db	10	dup(' '), '$'

	endl	db	0dh, 0ah, '$'

	

.code

main proc

	mov ax, @data

	mov ds, ax

	

	lea si, string1

	

	mov ah, 1

READ_NEXT:

	int 21h

	cmp al, 13

	je NEXT

	mov [si], al

	inc si

	jmp READ_NEXT

	

NEXT:

	mov al, '$'

	mov [si], al

	dec si

	lea dx, endl

	mov ah, 9

	int 21h

	

	lea di, string1

BEG:

	mov bx, [di]

	mov bp, [si]

	mov [di], bp

	mov [si], bx

	dec si

	inc di

	cmp di, si

	jl BEG

	

	lea dx, string1

	int 21h

	lea dx, endl

	int 21h

	

	mov ah, 4ch

	int 21h

	

main endp

end main

[RhetoricalRuvim]

At the area where it is:

BEG:

	mov bx, [di]

	mov bp, [si]

	mov [di], bp

	mov [si], bx

	dec si

	inc di

	cmp di, si

	jl BEG

would it work if you use 'al' and 'ah', instead of 'bx' and 'bp'?

Edited by dargueta, 14 December 2010 - 10:10 PM.

[dargueta]

Ooh, dude...don't use BP like that. You could cause some serious stack issues if you pass arguments using the stack, especially with external functions. RR is right, though.

[assembler_wanna_be]

Thanks for the quick response!