Progr           segment
                assume  cs:Progr, ds:dane, ss:stosik

start:          mov     ax,dane
                mov     ds,ax
                mov     ax,stosik
                mov     ss,ax
                mov     sp,offset szczyt

    next_digit:
                ; get char from keyboard
                ; into AL:
                MOV     AH, 00h
                INT     16h
                ; and print it:
                MOV     AH, 0Eh
                INT     10h

                ; check for MINUS:
                CMP     AL, '-'
                JE      set_minus

                ; check for ENTER key:
                CMP     AL, 13  ; carriage return?
                JNE     not_cr
                JMP     stop_input

    not_cr:
                jmp    backspace_checked


backspace_checked:
                ; allow only digits:
                CMP     AL, '0'
                JAE     ok_AE_0

ok_AE_0:
                CMP     AL, '9'
                JBE     ok_digit
                ;todo skok że nie jest cyfrą
ok_digit:
                ; multiply CX by 10 (first time the result is zero)
                PUSH    AX
                MOV     AX, CX
                MUL     CS:ten                  ; DX:AX = AX*10
                MOV     CX, AX
                POP     AX
                ; convert from ASCII code:
                SUB     AL, 30h
                ; add AL to CX:
                MOV     AH, 0
                ADD     CX, AX
                                   ;todo jump if the number is too big.
                JMP     next_digit

set_minus:
                MOV     CS:make_minus, 1
                JMP     next_digit

stop_input:
                ; check flag:
                CMP     CS:make_minus, 0
                JE      print_hex
                NEG     CX
                jmp print_hex



print_hex:
                mov bl, cl      ;in cl is stored number
                mov cx, 4
            .print_digit:
                    rol bx, 4   ; move the currently left-most digit into the least significant 4 bits
                    mov dx,bx
                    and dx, 15  ; isolate the hex digit we want to print
                    add dx,30h  ; and convert it into a character..
                    cmp dx,'9'  ; ...
                    jbe .ok     ; ...
                    add dx,7    ; ... (for 'A'..'F')
                .ok:            ; ...
                    mov ah,2h    ; INT 21H / AH=2: write character to stdout
                    int 21h
                    loop .print_digit

                    MOV AH, 4CH
                    MOV AL, 01  ;your return code.
                    INT 21H

Progr           ends

dane            segment
make_minus      DB      ?       ; used as a flag.
ten             DW      10      ; used as multiplier.
dane            ends

stosik          segment
                dw    100h dup(0)
szczyt          Label word
stosik          ends

end start