The system clock is updated at ever

The system clock is updated at every clock interrupt. If interrupts were disabled—particularly for a long period of time—it is possible the system clock could easily lose the correct time. The system clock is alsousedforschedulingpurposes.Forexample,thetimequantumfora processisexpressedasanumberofclockticks.Ateveryclockinterrupt, the schedulerdeterminesif the time quantum for the currentlyrunning process has expired. If clock interrupts were disabled, the scheduler couldnotaccuratelyassigntimequantums.Thiseffectcanbeminimized by disabling clock interruptsfor only very short periods.