RSTS/E
Operating system
RSTS is a multi-user time-sharing operating system developed by Digital Equipment Corporation for the PDP-11 series of 16-bit minicomputers. The first version of RSTS was implemented in 1970 by DEC software engineers that developed the TSS-8... Wikipedia
Default user interface: Command-line interface: DCL (Digital Command Language)
Source model: Closed source
Written in: MACRO-11 assembly language, BASIC-PLUS-2, DCL