RSTS/E

RSTS is a multi-user time sharing operating system that Digital Equipment Corporation built for its PDP-11 minicomputers, first implemented in 1970, with its final version, RSTS/E 10.1, shipped in September 1992. DEC sold its PDP-11 software business in 1994, after which Mentec continued supporting later versions. The system ran only on PDP-11 hardware, from the PDP-11/20 through the PDP-11/70, was written mainly in MACRO-11 assembly language with its utilities in BASIC-PLUS, and could support up to 128 terminals and 63 concurrent jobs. Memory support grew from 56 kilobytes in early versions to 4 megabytes in later ones, and starting with version 9 it added the Digital Command Language as its primary command interface, alongside support for FORTRAN, COBOL and DIBOL through runtime emulation. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/