;screen shot appears at bottom.
;note these features: arrays declared and NOT initialized
(ie. assume they hold junk)
; usin
g stack: pushes and pops
;dos functions to read and write strings to/from the terminal
.MODEL SMALL
.STACK 100h
.DATA
MAX EQU 80
prompt db 'enter a string',0ah,0dh,'$'
outpt db 'and your output....',0ah,0dh,'$'
StringToReverse DB MAX DUP(?)
ReverseString DB MAX DUP(?)
.CODE
start:
mov ax,@data
&nb
sp; mov ds,ax
;set DS to point to the data segment
mov ah,9
mov dx,offset prompt
int 21h
mov ah,3fh
;DOS read from handle function #
; mov bx,0
;standard input handle
mov cx,MAX
;read up to maximum number of characters
mov dx,OFFSET StringToReverse ;store
the string here
int 21h &nb
sp;
;get the string
and ax,ax
;were any characters read?
jz Done
;no, so you're done
mov cx,ax &
nbsp;
;put string length in CX, where
; you can use it as a counter
push cx &nb
sp;
;save the string length
mov bx,OFFSET StringToReverse
mov si,OFFSET ReverseString
add si,cx
dec si
;point to the end of the
;
; reverse string buffer
ReverseLoop:
mov al,[bx]
;get the next character
mov [si],al
;
;store the characters in reverse order
inc bx
;point to next character
dec si
;point to previous location in reverse buffer
loop Revers
eLoop
;move next character, if any
mov ah,9
mov dx,offset outpt
int 21h
pop cx
;get back the string length
mov ah,40h &nb
sp;
;DOS write from handle function #
mov bx,1
;standard output handle
mov dx,OFFSET ReverseString
;print this string
int 21h
;print the reversed string
Done:
mov al,0
mov ah,4ch
;DOS terminate program function #
int 21h &n
bsp;
;terminate the program
END start
end