A new program for simulation of X-ray diffraction patterns of polycrystalline materials with different kinds of imperfections has been developed. These calculations are performed on the base of the model of one-dimensional (1D) disordered crystal being the statistical sequence of the biperiodic layers. Each layer is characterized by its structure, thickness and probability of occurrence. The sequence of layers is specified with the use of order-disorder parameters and some probability coefficients. Such defects as small sizes of coherently scattering domains (CSD), microstrains and stacking faults are taken into account. Our program simulates two kinds of layers: isotropic (circle) and anisotropic (rectangle). Along with mean sizes of CSD, the variances of normal or lognormal size distributions of CSD can be taken into account. Also, the program makes it possible to specify whether the fluctuations in the layer position are correlated or not. The plane groups of symmetry are introduced to reduce the run time. The background is approximated by using the smoothing spline-functions. The correction for instrumental line broadening is calculated with a standard. Simulated diffraction pattern is compared and fitted for best correspondence with the experimental one. Real structures of some specimens have been investigated with this program. These are metastable Ni-In alloys prepared by mechanochemical synthesis, filamentary carbons and metallic Co with microdomain structure.