org 100h
Start:
        mov ah, $09
        mov dx, DispText
        int 21h

        mov dx, NewLine
        int 21h

        mov ah, 0ah
        mov dx, bufStr
        int 21h

        mov ah, $09
        mov dx, NewLine
        int 21h


        mov ah, [bufStr + 6]
        mov dh, [bufStr + 5]
        mov [bufStr + 6], dh
        mov [bufStr + 5], ah
        mov [bufStr + 11], '$'

        mov dh, [bufStr + 10]
        sub dh, [bufStr + 9]
        add [bufStr + 7], dh


        mov ah, $09
        mov dx, bufStr
        int 21h
        mov dx, NewLine
        int 21h

        mov ah, $08
        int 21h

        ret

DispText   db  "Please, enter 9 letters$"
NewLine    db   0dH, 0aH, "$"
bufStr     db  10, 0, 10 dup(?)