This document describes how to install and write a C++ program using Giac computer algebra software. This assumes you already have C++ installed on your PC. I did this on a Linux OS.
Here is a post about the history of Giac.
The help pages that describes the giac commands are now at github https://github.com/geogebra/giac/tree/master
These old pages are gone https://www-fourier.ujf-grenoble.fr/~parisse/giac/doc/en/cascmd_en/cascmd_en.html and https://www-fourier.ujf-grenoble.fr/~parisse/giac/cascmd_en.pdf