Computations of convolution coefficient matrices (CCM) for multidimensional least-squares filters are challenging, as their standard numerical computations using computer programming languages suffer from large floating-point truncation errors, which severely degrade the accuracy. As the spatial dimension, the kernel size, and the polynomial order increase, these errors grow and become as large as some genuine elements of the CCM. This open source software - PCCC - handles these issues adequately, by employing rational number arithmetic. The CCM is obtained in the rational number format (i.e. in the p/q format), which is fully accurate. The rational number CCM elements are converted into floating point format also, until any pre-defined number of significant digits. Important features of PCCC are as follows: It can handle both structured and unstructured kernels of arbitrary size and shape with randomly distributed nodes It can handle extremely stretched kernel nodes, even where distance between adjacent nodes vary by several hundred orders of magnitudes It can handle arbitrary weights that can be given to the sampled values at different kernel nodes It can handle both symmetric and asymmetric polynomials of arbitrary orders It can calculate fully accurate CCMs (in the rational number format) Fast computation using OpenMP parallelization DOWNLOADS: pccc-0.8.1-Win-Setup.exe : Setup file to install on 64-bits Microsoft Windows. Can be installed on Unix-like systems also, in Wine environment. Tested OS's: Windows 7 and Fedora-27, 28. Tested processors: Intel's i5 and AMD's A9. pccc-0.8-1.x86_64.rpm : RPM package for installation on 64-bits Unix-like systems. Tested OS's: Fedora-27, 28. Tested processors: Intel's i5 and AMD's A9. pccc-0.8-1.src.rpm : Source RPM for rebuilding packages on Unix-like systems. Used to build the above RPM package. pccc-0.8.tar.gz : Source code, with compilation and installation instructions. Used to build all the aforementioned packages. Tested OS's: 64-bits Windows-7 in MSYS+MinGW environment and 64-bits Fedora-27. Tested processor: Intel's i5. If you are interested in testing the software on other operating systems, or would like to make its DEB packages, or encounter any bug in the software, please contact me. CONTACT: Dr. Chandra Shekhar E-mail: chandra.s.iitk@gmail.com Homepage: https://sites.google.com/site/ChandraAcads Please visit the homepage for most recent updates.