There are two programs installed by the instructions in Download and Install. The older one Fokko is designed for doing single (perhaps large) computations: in the command line interface, the user can issue single commands (for example, “compute all of the Kazhdan-Lusztig polynomials for a split group of type E7”). This program was begun by Fokko du Cloux in 2004 and 2005. Since 2006 it has been developed primarily by Marc van Leeuwen, with contributions by Alfred Noel, Jeff Adams, and others.
The program atlas is designed for interactive exploration of real reductive Lie groups and their representations. It has been developed by Marc van Leeuwen since 2006. It is built on a programming language axis, also developed by Marc van Leeuwen. The atlas software invokes (invisibly to the user!) the libraries of Fokko to create mathematical objects; then the axis language offers standard programming tools (loops, variables, scripts, and so on) with which the user can manipulate them. An important part of atlas is the (constantly growing) library of predefined scripts, which can be used or modified to do interesting mathematical tasks. This library has been developed by Marc van Leeuwen, Jeff Adams, Annegret Paul, and others.