CR equ 13
LF equ 10
 
    JMP START
 
prompt    db    CR,LF,'Please enter a word to be checked:  $'
outmsg    db    CR,LF,'The reverse word is:  $'
instring  db    12,?,'              $'
outstring db    '????????????$'
correct   db    CR,LF,'The word that you have entered is a palindrome$'
incorrect db    CR,LF,'The word that you have entered is not a palindrome$'
firstchar dw     ?
 
START:
 
    LEA DX,prompt
    MOV AH,9
    INT 21h
 
    LEA DX,instring
    MOV AH,0ah
    INT 21h
 
    LEA SI,instring
    MOV BL,byte ptr[SI + 1]
    INC BL
    MOV BH,0
    ADD SI,BX
    LEA firstchar,instring+2
 
    LEA DI,outstring
 
MOVECHAR:
 
    MOV BH,byte ptr[SI]
    MOV byte ptr[DI],BH
    CMP SI,firstchar
    JE DONE
    DEC SI
    INC DI
    JMP MOVECHAR
 
DONE:
 
    INC DI
    MOV byte ptr[DI],'$'
    LEA DX, outmsg
    MOV AH,9
    INT 21h
    LEA DX,outstring
    MOV AH,9
    INT 21h
 
FINISH:   
 
    MOV AH,4ch
    INT 21h

 
xor ch,ch                           ;clear ch
lea di, instring
mov cl, [ di + 1 ]                ;cx = length of string
mov di,ds                                
mov es,di                          ;es -> data segment
lea di, outstring                  ;es:di -> output string
mov si, offset instring + 2   ;ds:si -> input string
repe cmpsb                     ;compare strings (abort as soon as two
                              ;characters fail to match)
je                            ;jump to relevant code if strings are the same