RSTS/E
RSTS (pronounced as "RIST-ess" or "RIST-uhs") is a multi-user time-sharing operating system, developed by Digital Equipment Corporation ("DEC"), (now part of Hewlett Packard) for the PDP-11 series of 16-bit minicomputers. The first version of RSTS (RSTS-11, Version 1) was implemented in 1970 by DEC software engineers that developed the TSS-8 time-sharing operating system for the PDP-8. The last version of RSTS (RSTS/E, Version 10.1) was released in September 1992. RSTS-11 and RSTS/E are usually referred to just as "RSTS" and this article will generally use the shorter form.
Read more about RSTS/E: Acronyms and Abbreviations, Documentation, Features, History, Run-Time Environments, Add-ons By Other Companies, Applications