ALGOL 68RS is the second ALGOL 68 compiler written by I.F. Currie and J.D. Morrison at the Royal Signals and Radar Establishment. Unlike the earlier ALGOL 68R it was designed as a portable compiler and implemented the language of the revised Report.
Versions of ALGOL 68RS were written for the ICL 2900 Series, Multics and VAX/VMS.
Subsequently portions of this compiler were put into the public domain - as an ALGOL 68 to C translator - as part of the public release of ELLA.
Read more about ALGOL 68RS: History, Restrictions in The Language Compiled, Availability