org     100h
        jmp Start

function_print:
        mov     ah, $09
        int     21h
        ret

function_println:
        call    function_print
        mov     dx, LF
        call    function_print
        ret

function_print_LF:
        mov     ah, $09                 ;printing LF
        mov     dx, LF
        int     21h
        ret

function_read:
        mov     ah, $0A                 ;reading string
        int     21h
        ret

function_read_cbuf:
        mov     ax, $0C0A
        int     21h
        ret

function_await_input:
        mov     ax, $0C08
        int     21h
        test    al, al
        jnz     @F
        mov     ah, $08
        int     21h
@@:
        ret

Start:
        mov     dx, promptMessage
        call    function_println

        mov     dx, string
        call    function_read_cbuf

        call    function_print_LF

        mov     al, [string + 3]        ;swapping 2 and 4
        mov     ah, [string + 5]
        mov     [string + 5], al
        mov     [string + 3], ah

        mov     al, [string + 8]        ;changing 7
        add     al, [string + 7]
        sub     al, [string + 2]
        mov     [string + 8], al

        mov     dx, string + 2
        call    function_println

        call    function_await_input

        ret


promptMessage   db 'Please enter string$'
string          db 21, 0, 21 dup('$')
LF              db 10, '$'