  We solve a longstanding problem--determining structural information for
disordered materials from their diffraction spectra--for the case of planar
disorder in close-packed structures (CPSs). Our solution offers the most
complete possible statistical description of the disorder, and, from it, we
find the minimum effective memory length of disordered stacking sequences. We
also compare our model of disorder with the so-called fault model (FM) and
demonstrate that in simple cases our approach reduces to the FM, but in cases
that are more complex it provides a general and more accurate structural
description than the FM. We demonstrate our technique on two previously
published zinc sulphide diffraction spectra.
