Editing Fractional-order integrator (section)

== Digital devices ==
Digital devices have the advantage of being versatile, and are not susceptible to unexpected output variation due to heat or noise. The discrete nature of a computer however, does not allow for all of history to be computed. Some finite range [a,t] must exist. Therefore, the number of data points that can be stored in memory (''N''), determines the oldest data point in memory, so that the value a is never more than ''N'' samples old. The effect is that any history older than a is ''completely'' forgotten, and no longer influences the output.

A solution to this problem is the Coopmans approximation, which allows old data to be forgotten more gracefully (though still with exponential decay, rather than with the power law decay of a purely [[analog device]]).