The Pari system

Pari-gp is a software package for computer-aided number theory. It consists of a C library, libpari (with optional assembler cores for some popular architectures), and of the programmable interactive gp calculator. While you can write your own libpari-based programs, many people just start up a gp session, or have gp execute their scripts. Pari sessions can now be started inside TeXmacs.

Originally developed at Bordeaux by a team led by Henri Cohen, PARI-GP is now maintained by Karim Belabas at the Université Paris-Sud Orsay with the help of many volunteer contributors.