GPSS 50 years old, but still young

In 2011, GPSS, the General Purpose Simulation System, celebrates its 50^th anniversary. At the 2001 Winter Simulation Conference there were two papers dealing with the 40^th anniversary of GPSS. With these papers available on the Web, this paper will concentrate on the developments of GPSS after 2001. There are still three systems with the GPSS name that are sold, supported and improved: GPSS/H, GPSS World and the educational aGPSS systems family. There has also been a substantial development of the successor of GPSS/H, SLX. Finally, Proof Animation, which is closely connected to some of the GPSS systems, has been substantially improved during the last decade.