This page and the following contain the description of the features of ALICE Off-line environment.
The ALICE Off-line Project has started developing the current framework in 1998. The decision was taken at the time to build the simulation tool for the Technical Design Reports of the ALICE detector using the OO programming technique and C++ as an implementation language.
This lead us to the choice of ROOT as framework and GEANT 3.21 as simulation code. A prototype was quickly built and put in production. The experience with this was positive, and in November 1998 the ALICE Off-line project adopted ROOT as the official framework of ALICE Off-line.
AliRoot is the name of ALICE Run1/Run2 Off-line framework for simulation and reconstruction, while AliPhysics contains the analysis code. It uses the ROOT system as a foundation on which the framework and all applications are built.
Except for some remaining legacy Fortran code, this framework is based on the Object Oriented programming paradigm, and it is written in C++.
Please refer to the official installation instructions page.