RSTS () 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. RSTS-11 supports the BASIC programming language, an extended version called BASIC-PLUS, developed under contract by Evans Griffiths & Hart of Boston. Starting with RSTS/E version 5B, DEC added support for additional programming languages by emulating the execution environment of the RT-11 and RSX-11 operating systems. Acronyms and abbreviations BTSS (Basic Time Sharing System – never marketed) – The first name for RSTS. CCL (Concise Command Language) – equivalent to a command to run a program kept in the Command Line Interpreter. CIL (Core Image Library) – A container file format used to hold one or more standalone (bootable) programs and operating systems, such as RSTS through version 6A. CILUS (Core Image Library Update and Save) – DOS-11 program to manipulate a CIL file. CLI (Command Line Interpreter) – See Command-line interface. CUSPs (Commonly Used System Programs) – System management applications like Task Manager or Registry Editor on Microsoft Windows. On RSTS-11, CUSPs were written in BASIC-Plus just like user programs. DCL (Digital Command Language) – See DIGITAL Command Language. DTR (DATATRIEVE) – programming language FIP (File Information Processing) – resident area for issuing file requests FIRQB (File Information Request Queue Block) – A data structure containing information about file requests. KBM (Keyboard Monitor) – Analogous to Command Line Interpreter. LAT (Local Area Transport) – Digital's predecessor to TCP/IP MFD (Master File Directory) – Root directory of file system. PBS (Print Batch Services) PIP (Peripheral Interchange Program) PPN (Project Programmer Number) – Analogous to GID and UID in Unix. RDC (Remote Diagnostics Console) – A replacement front panel for a PDP-11 which used a serial connection to the console terminal or a modem instead of lights and toggle switches to control the CPU. RSTS-11 (Resource Sharing Time Sharing System) – The first commercial product name for RSTS RSTS/E (Resource Sharing Timesharing System Extended) – The current implementation of RSTS. RTS (Run Time System) – Read only segment of