Summary of changes from v1.0 to v2.0 (J.Kobus 05.2011) This note concerns the two-dimensional finite difference Hartree-Fock program (x2dhf) that has been prepared for publication in Comp. Phys. Commun. to update its previous version published in 1996 (referred to as version 1.0). The program has been constantly changed/improved over the years. The present version of the program had its code overhauled with corrections/modification introduced in dozens of places in hope that accuracy, functionality and readability of the program would be improved. These are some of the changes that have been introduced since the last update (January 2001) of the program: - The program can be used for the calculation of electrical properties by means of the finite electric field method. Perl scripts has been added to ease extraction of data from output files in order to calculate polarizabilities and hyperpolarizabilities (see util/runelprop.pl and util/elprop.pl). - The rate of convergence of the SCF/SOR iterations is very much dependent on the values of overrelaxation parameters for orbitals and potentials. Due to a semi-empirical formula it is now possible to set automatically the overrelaxation parameter for relaxation of both orbitals and Coulomb and exchange potentials to a near optimal value (see User's Guide for details). Since for large systems some 90% of the CPU goes into relaxation of the potentials a proper choice of the relaxation parameter can speedup calculations substantially. - Sometimes the convergence threshold (for energy and/or normalization) is set too low and cannot be satisfied on a given grid and as a result the SCF/SOR process continues in vain. Now the iterations are stopped if orbital energies or orbital norms display no improvment over a given number of the most recent iterations, respectively (see description of label CONV in User's Guide for details). - Evaluation of boundary conditions for potentials have been modified resulting in a higher accuracy of solutions for a given value of the practical infinity. - The grid specification has been simplified. Now one needs to define the number of grid points in nu variable and the value of the practical infinity. The number of grid points in mu variable is calculated so as to make the discretization errors in these variables comparable. - The compilation/installation process has been simplified by controlling it through a new Makefile (checked with GNU Make, version 3.79.1, and GNU bash, version 2.05b.0(1)) which allows to set/change easily all the required variables and update the source files and the executable accordingly (there is no need to use a separate 'make_sources.2dhf file any more). See INSTALL for details. - The x2dhf program can be compiled to support calculation using three different combinations of integer/real data types: i32 (4-byte integers, 8-byte reals), i64 (8-byte integers, 8-byte reals) and r128 (8-byte integers, 16-byte reals); see src/Makefile for details. In order to facilitate exchange of binary data generated on machines of~different architectures or using different compilers it is now possible to export/import data in formatted instead of unformatted form. - Usage of multiple grids is no longer supported.