First hits in google: https://openmodelica.org/index.php/forum/topic?id=434
The dataInfo matrix corresponds to names and descriptions. It contains the data_n matrix, column number, interpolation and something else (Dymola knows; probably discrete variables). The dataClass matrix contains some info if the data_2 matrix is transposed or not, some version number for Dymola features.

Many thanks.
I should have googled the query myself.

Ehm,
if I understand well, the link tells how to interpret the mat file from Matlab or Octave, or when using python.
What I would like, instead, is to create my own program that reads these files. I program in C++ using Qt.
How OM writes and reads mat files? using C coding or some dll from Mathworks?

Since the files outputted by OM contain character variables the used matlab format must be later than (the very old but still used) 4.0. But which one? Where to find details of the format?

You should be able to use http://www.mathworks.se/help/pdf_doc/ma … format.pdf (the last pages)
We use our own C implementation (which has a BSD-license option): https://openmodelica.org/svn/OpenModeli … _matlab4.c

Good!
that is what I needed.
thank you.

Good!
that is what I needed.
thank you.