问题
here is my code:
model small
stack 100h
.data
string1 db "Khoa$"
string2 db 4 dup(?)
count dw 4
.code
begin:
mov ax,@data
mov ds,ax
mov es,ax
mov cx,count
mov si,0
mov di,0
add di,count
dec di
again: mov al,string1[si]
mov string2[di],al
inc si
dec di
loop again
mov ah,9
lea dx,string1
int 21h
end begin
in this part
mov ah,9
lea dx,string1
int 21h
when i try to display string1 to console, it's ok. but no result with string2.
i'm new to assembly. Please help!
回答1:
Although this is homework, this is a reasonable attempt at a solution. I don't know what assembler you are using - it looks like MASM but I'm unsure how these 2 lines could assemble without a syntax error:
model small
stack 100h
I think this should be (note the periods in front as they are assembler directives):
.model small
.stack 100h
string1 is initially 5 characters long including the $ to terminate the string. When using int 21h/ah 9 strings need to be terminated with $ or it will continue to print junk beyond the end of your string. With that in mind your output buffer should be long enough to hold 5 characters including the $
so string2 should be defined as:
string2 db 5 dup(?)
The primary problem in your code is terminating the string with a $. One way would be to place the $ in the last position of the array when you set up the si and di registers initially:
mov si,0
mov di,0
add di,count
mov string2[di],'$' ; Put string terminator in last position
dec di
Also note:
mov di,0
add di,count
Could be written simply as:
mov di, count
If you are using MASM, to gracefully exit your 16 bit program you might want to put a .exit directive just before your end statement:
.exit
end begin
来源：https://stackoverflow.com/questions/32568014/trouble-when-reverse-and-display-string-in-assembly