[en] 1 - Description of program or function: This version of DORT (ORNL Mod 5, 12 Oct 89, INEL Ver 2.1) was derived from the Cray UNICOS version distributed in CCC-543/TORT, which was developed at ORNL under Defense Nuclear Agency sponsorship. DORT is directly based on the earlier DOT codes. DORT-PC determines the fluence of particles throughout one- or two-dimensional geometric systems due to sources either generated as a result of particle interaction with the medium or incident upon the system from extraneous sources. The principal application is to the deep-penetration transport of neutrons and photons. Criticality (k-type and search) problems can also be solved. Numerous printed edits of the results are available, and results can be transferred to output files for subsequent analysis. 2 - Method of solution: The Boltzmann transport equation is solved, using either the method of discrete ordinates or diffusion theory approximation. In the discrete ordinates method, the primary mode of operation, balance equations are solved for the flow of particles moving in a set of discrete directions in each cell of a space mesh and in each group of a multigroup energy structure. Iterations are performed until all implicitness in the coupling of cells, directions, groups, and source regeneration has been resolved. Several methods are available to accelerate convergence. Anisotropic cross sections can be expressed in a Legendre expansion of arbitrary order. Output data sets can be used to provide an accurate restart of a previous problem or to deliver information to other codes. Several techniques are available to remove the effects of negative fluxes caused by the finite difference approximation and of negative scattering sources due to truncation of the cross-section expansion. The space mesh can be described such that the number of first-dimensional (i) intervals varies with the second dimension (j). The number of discrete directions can vary across the space mesh and with energy. Direction sets can be biased, with discrete directions concentrated such as to give fine detail to streaming phenomena. 3 - Restrictions on the complexity of the problem: External force fields or nonlinear effects cannot be treated. Flexible dimensioning is used throughout so that no restrictions are imposed on individual problem parameters. Certain options, especially diffusion theory, are not compatible with variable mesh and quadrature problems