Int 1Ch                 User Timer Tick

    Called at every timer tick (18.2 times per second, or every 55 ms)
    by Int 08h (System Timer).

    ──────────────────────────────────────────────────────────────────

    By default, the interrupt handler for this interrupt uses IRET to
    return to the caller. The user can supply his own handler so he
    can attain control at every timer tick.


    Note
    Note that this interrupt is called by the hardware timer interrupt
    (Int 08h), which has not signaled the end of the interrupt back to
    the interrupt controller. Therefore, this routine is limited in
    the actions it can take, since all interrupts will be disabled. A
    better approach to this problem is to intercept Int 08h. The new
    Int 08h handler will first call the standard Int 08h, which will
    handle the interrupt controller completion signals mentioned
    above. Then after the standard Int 08h is completed, the new
    handler can do whatever it has to do at every timer tick.