Int 4Ah                 User Alarm                    XT-286, AT, Convertible

    Called by the Real-Time Clock (RTC) interrupt handler when the
    real- time clock alarm conditions are met.

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    By default, the interrupt handler for this interrupt IRETs to the
    caller. The user can supply a handler that will gain control
    whenever the current time is equal to the alarm time. Make sure
    this interrupt handler is installed before using Int 1Ah, Service
    06h, to set the real-time clock alarm.


    Note
    This service is available only for the AT, XT-286, and PC
    Convertible.

    The Real-Time Clock (RTC) interrupt handler is Int 70h for the AT
    and XT-286. The PC Convertible uses Int 08h (System Timer).