Previous versions

History and previous versions


Our first program (1993) replacing tables of probability distributions, was running on the command line under MS-DOS. It was written in Pascal by Sytse Knypstra and Arjen Merckens. In fact it was a combination of a calculator and a replacement of probability tables. Its interface language was Dutch.


Download the compressed file (50 kB), unzip it and start PCalc.exe under the program DOSBox.

Screenshot of PCalc
Screenshot of PCalc


Around the year 2000 PQRS (Probabilities, Quantiles and Random Samples) was designed as a successor to PCalc with a graphical user interface. PQRS was written in Delphi and runs under Windows and - with the help of Wine - under Linux.


Download the compressed file (0.7 MB), unzip it and start PQRS.exe.

Screenshot of PQRS 2
Screenshot of PQRS 2


In 2013 PQRS was rewritten in Python. In order to distinguish it from the previous PQRS version, and as a tribute to Python and its author, Guido van Rossem, the first letter in its name was replaced by 'Py'.

PyQRS 4.0

PyQRS 4.0 (March 2016) is functionally equivalent to its predecessor PyQRS 3. It runs on Android (mobile) devices. The app is written in Python using the Kivy framework.

PyQRS 4.1

PyQRS 4.1 (June 2017) has an improved user interface over its predecessor PyQRS 4.0. It runs on Android (mobile) devices, and on the Linux (64 bits) and Windows (64 bits) platforms.
Screenshots can be found under Using PyQRS.

PyQRS 4.2

In 2021 version 4.2 was published after a part of the source code had been rewritten and a few bugs were fixed. Screenshots are shown on the main page of PyQRS.