; multi-segment executable file template.

data segment
    ; add your data here!
    pkey db "press any key...$"
    msg1 db "Enter string: $"
    msg2 db "Input: $"
    msg3 db "Output: $"
    cr db 0Ah, 0Dh, '$'
    buff db 200
    length db ?
    buffer db 200 dup ('$')
ends

stack segment
    dw   128  dup(0)
ends

code segment
start:
; set segment registers:
    mov ax, data
    mov ds, ax
    mov es, ax
    
    call input_string
    
    
    lea bx, buffer  
    mov cx, bx
    mov al, [bx]     ;get first char to compare
l1:                  
    inc bx           ;increment second char pointer
    
    cmp [bx], 0Dh    ;check for end-of-line
    je l3            ;if end - change first char
    mov ah, [bx]     ;get second char 
    cmp ah,al        ;compare, if second is greater than first
    jae l1           ;if no, skip exchange
    mov [bx], al     ;exchanging
    xchg bx, cx
    mov [bx], ah
    xchg ah, al
    xchg bx, cx  
    jmp l1           ;repeat

l3: inc cx           ;increment first char pointer
    mov bx, cx       ;set second char pointer equal to the first
    cmp [bx] ,0Dh    ;check for end-of-line
    je exit          ;if end - go to end
    mov al, [bx]     ;get first char to compare
    jmp l1           ;repeat
    
    
   
input_string:
    lea dx, msg1
    mov ah, 9
    int 21h
    lea dx, buff 
    mov ah, 0Ah
    int 21h      
    lea dx, cr 
    mov ah, 9
    int 21h
    lea dx, msg2 
    mov ah, 9
    int 21h
    lea dx, buffer
    mov ah, 9
    int 21h
    lea dx, cr 
    mov ah, 9
    int 21h
    ret
       
    ; add your code here
exit:            
    lea dx, msg3
    mov ah, 9
    int 21h
    lea dx, buffer
    mov ah, 9
    int 21h
    lea dx, cr
    mov ah, 9
    int 21h
    
    lea dx, pkey
    mov ah, 9
    int 21h        ; output string at ds:dx
    
    ; wait for any key....    
    mov ah, 1
    int 21h
    
    mov ax, 4c00h ; exit to operating system.
    int 21h    
ends

end start ; set entry point and stop the assembler.