Data Segment
  num db 00000010B
Data Ends

Code Segment
  Assume cs:code, ds:data

  Begin:
    mov ax, data
    mov ds, ax
    mov es, ax
    mov ah, 0000h
    mov al, num
    NOT al
    mov bl, al
    adc al, 00000001B
    mov bl, al

  Exit:
    mov ax, 4c00h
    int 21h
Code Ends
End Begin