swap two input using [xchg]

swap.asm

;SWAP two input using xchg
        
        .model small
        .stack 100h
        .data
             
             a db '[a] : $'
             b db '[b] : $'
             a_in db ?
             b_in db ?
             
        .code 
        
            main proc 
               
             ;input part   
             
             mov ax,@data       ;prepare data segment
             mov ds,ax
             
             mov ah,09h         ;print string
             lea dx,a
             int 21h
             
             mov ah,01h         ;input char
             int 21h
             mov a_in,al
             
             mov ah,02h         ;tab
             mov dl,09h
             int 21h
             
             mov ah,09h         ;string print
             lea dx,b
             int 21h
            
             mov ah,01h         ;input char
             int 21h  
             
             xchg a_in,al
             mov b_in,al
             
             ;output part
             
             mov ah,02h         ;newline
             mov dl,0Ah
             int 21h
             mov dl,0Dh
             int 21h
             
             mov ah,09h         ;string print
             lea dx,a
             int 21h
             
             mov ah,02h         ;char output
             mov dl,a_in
             int 21h
             
             mov dl,09h         ;tab
             int 21h
             
             mov ah,09h         ;string print
             lea dx,b           
             int 21h
             
             mov ah,02h         ;char output
             mov dl,b_in
             int 21h
             
           
             mov ah,4ch         ;terminate
             int 21h
             
          main endp
          end main