org 100h

        ;print_msg
                mov dx, helloString
                mov ah, $09
                int 21h
        ;change line
                mov     ah, $09
                mov     dx, nextLine
                int     21h
        ;read_str:
                mov     dx, bufferedString
                mov     ah, $0A
                int     21h
        ;change line
                mov     ah, $09
                mov     dx, nextLine
                int     21h
        ;Check_Length
                cmp     [bufferedString+1], 2
                jle      No
        ;Compare
                mov     dh,  [bufferedString+4]
                cmp     [bufferedString+2], dh
                jnz     No
        ;IsDigit
                mov     ch, [bufferedString+3]
                cmp     ch, '0'
                jb      No
                cmp     ch, '9'
                jg      No
        ;IsLetter
                movsx     si, [bufferedString+1]
                sub     si, 1
                mov     ch, [bufferedString+si]
                cmp     ch, 'A'
                jb      No
                cmp     ch, 'Z'
                jg      No
        ;print_msg_Yes
                mov     dx, answerYes
                mov     ah, $09
                int     21h
                jmp     EndLine
        ;print_msg_No
        No:
                mov dx, answerNo
                mov ah, $09
                int 21h

        ;end
        EndLine:
                ret

;---------------------
helloString db "Enter a string:$"
bufferedString db 11, 0, 10 dup(?), '$'
nextLine db 13,10,"$"
answerYes db "Yes$"
answerNo  db "No$"