{"history":[],"article":{"id":"fb4379eb-c3cf-4cc8-a295-cc884f7a1419","title":"RSTS/E","slug":"rsts-e","content":":::summary\n![RSTS/E 10.1, running the DCL CLI](https://upload.wikimedia.org/wikipedia/commons/d/d0/Rsts///Spike.png)\n**Name:** RSTS \n**Screenshot:** Rstse-10 1.png \n**Developer:** [Digital Equipment Corporation](https://bliptext.com/articles/digital-equipment-corporation), later [Mentec](https://bliptext.com/articles/mentec-international-ltd) \n**Source Model:** [Closed source](https://bliptext.com/articles/closed-source) \n**Kernel Type:** [Time-sharing](https://bliptext.com/articles/time-sharing) [operating systems](https://bliptext.com/articles/operating-system) \n**Supported Platforms:** [PDP-11](https://bliptext.com/articles/pdp-11) \n**Ui:** [Command-line interface](https://bliptext.com/articles/command-line-interface): [DCL (Digital Command Language)](https://bliptext.com/articles/digital-command-language) \n**Released:** 1970 \n**Latest Release Version:** RSTS V10.1 \n**Latest Release Date:** 1992 \n**Language:** [English](https://bliptext.com/articles/english-language) \n**Programmed In:** [MACRO-11](https://bliptext.com/articles/macro-11) [assembly language](https://bliptext.com/articles/assembly-language), [BASIC-PLUS](https://bliptext.com/articles/basic-plus)-2, [DCL](https://bliptext.com/articles/digital-command-language) \n**Prog Language:** [ALGOL-60](https://bliptext.com/articles/algol), [APL](https://bliptext.com/articles/apl-programming-language), [BASIC-PLUS](https://bliptext.com/articles/basic-plus), [BASIC-PLUS](https://bliptext.com/articles/basic-plus)-2, [C](https://bliptext.com/articles/c-programming-language), [C](https://bliptext.com/articles/c-programming-language)OBOL, [DATATRIEVE](https://bliptext.com/articles/datatrieve), [DIBOL](https://bliptext.com/articles/dibol), [Forth](https://bliptext.com/articles/forth-programming-language), [Fortran](https://bliptext.com/articles/fortran), MA[C](https://bliptext.com/articles/c-programming-language)RO-11, [Pascal](https://bliptext.com/articles/pascal-programming-language), [RPG II](https://bliptext.com/articles/ibm-rpg), TE[C](https://bliptext.com/articles/c-programming-language)O \n**Updatemodel:** Binary patches, complete binaries \n**Package Manager:** BACKUP \n**Working State:** No development, still available \n**License:** [Proprietary](https://bliptext.com/articles/proprietary-software) \n**Preceded By:** [TSS/8](https://bliptext.com/articles/tss-8) \n:::\n\n# \n**RSTS** is a [multi-user](https://bliptext.com/articles/multi-user) [time-sharing](https://bliptext.com/articles/time-sharing) [operating system](https://bliptext.com/articles/operating-system) developed by [Digital Equipment Corporation](https://bliptext.com/articles/digital-equipment-corporation) (DEC, now part of [Hewlett-Packard](https://bliptext.com/articles/hewlett-packard)) for the [PDP-11](https://bliptext.com/articles/pdp-11) series of [16-bit](https://bliptext.com/articles/16-bit) [minicomputers](https://bliptext.com/articles/minicomputer).\nThe first version of RSTS (RSTS-11, [Version 1](https://bliptext.com/articles/)) was implemented in 1970 by DEC [software engineers](https://bliptext.com/articles/software-engineering) that developed the [TSS-8](https://bliptext.com/articles/tss-8) time-sharing operating system for the [PDP-8](https://bliptext.com/articles/pdp-8).\nThe last version of RSTS (RSTS/E, [Version 10.1](https://bliptext.com/articles/)) was released in September 1992.\nRSTS-11 and RSTS/E are usually referred to just as \"RSTS\" and this article will generally use the shorter form.\nRSTS-11 supports the BASIC programming language, an extended version called BASIC-PLUS, developed under contract by Evans Griffiths & Hart of Boston.\nStarting with RSTS/E version 5B, DEC added support for additional programming languages by emulating the execution environment of the [RT-11](https://bliptext.com/articles/rt-11) and [RSX-11](https://bliptext.com/articles/rsx-11) operating systems.\n\n# Acronyms and abbreviations\n\n# Development\n\n## 1970s\nThe [kernel](https://bliptext.com/articles/kernel-operating-system) of RSTS was [programmed](https://bliptext.com/articles/computer-[program](https://bliptext.com/articles/computer-program)ming) in the [assembly language](https://bliptext.com/articles/assembly-language) [MACRO-11](https://bliptext.com/articles/macro-11), [compiled](https://bliptext.com/articles/compiler) and [installed](https://bliptext.com/articles/installation-computer-[program](https://bliptext.com/articles/computer-program)s) to a [disk](https://bliptext.com/articles/hard-disk-drive) using the **[CILUS](https://bliptext.com/articles/dos-11)** [program](https://bliptext.com/articles/computer-program), running on a [DOS-11](https://bliptext.com/articles/dos-11) operating system.\nRSTS [booted](https://bliptext.com/articles/booting) into an extended version of the [BASIC](https://bliptext.com/articles/basic) programming language which DEC called \"[BASIC](https://bliptext.com/articles/basic)-PLUS\".\nAll of the [system software](https://bliptext.com/articles/system-software) **CUSPS** for the operating system, including the programs for resource accounting, [login](https://bliptext.com/articles/login), logout, and managing the system, were written in BASIC-PLUS.\nFrom 1970 to 1973, RSTS ran in only [56K bytes](https://bliptext.com/articles/kilobyte) of [magnetic core memory](https://bliptext.com/articles/magnetic-core-memory) (64 kilobytes including the [memory-mapped I/O](https://bliptext.com/articles/memory-mapped-i-o) space).\nThis would allow a system to have up to 16 [terminals](https://bliptext.com/articles/computer-terminal) with a maximum of 17 [jobs](https://bliptext.com/articles/job-computing).\nThe maximum program size was 16K bytes.\nBy the end of 1973 DEC estimated there were 150 [licensed](https://bliptext.com/articles/license) systems running RSTS.\nIn 1973, [memory management](https://bliptext.com/articles/memory-management) support was included in RSTS (now RSTS/E) for the newer DEC [PDP-11/40](https://bliptext.com/articles/pdp-11-40) and [PDP-11/45](https://bliptext.com/articles/pdp-11-45) minicomputers (the [PDP-11/20](https://bliptext.com/articles/pdp-11-20) was only supported under RSTS-11).\nThe introduction of memory management in the newer PDP-11 computers not only meant these machines were able to address four times the amount of memory (18-bit [addressing](https://bliptext.com/articles/addressing), 256K bytes), it also paved the way for the developers to separate [user mode](https://bliptext.com/articles/user-space) processes from the core of the kernel.\nIn 1975, memory management support was again updated for the newer 22-bit addressable [PDP-11/70](https://bliptext.com/articles/pdp-11-70).\nRSTS systems could now be expanded to use as much as two [megabytes](https://bliptext.com/articles/megabyte) of memory running up to 63 jobs.\nThe **[RTS](https://bliptext.com/articles/run-time-system)** and **[CCL](https://bliptext.com/articles/concise-command-language)** concepts were introduced although they had to be compiled in during \"[SYSGEN](https://bliptext.com/articles/system-generation)\".\nMulti-terminal service was introduced which would allow a single job the ability to control multiple terminals (128 total).\nLarge-message send/receive and interprocess communication became very sophisticated and efficient.\nBy August there are 1,200 licensed systems.\nIn 1977, the installation process for RSTS was no longer dependent on DOS-11.\nThe RSTS kernel could now be compiled under the [RT-11](https://bliptext.com/articles/rt-11) **RTS**, formatted as a kernel file with [RT-11](https://bliptext.com/articles/rt-11) **SILUS**, and [copied](https://bliptext.com/articles/copying) to the system or other disks, while the [computer](https://bliptext.com/articles/computer) was time-sharing.\nThe BASIC-PLUS ****RTS**** (as well as RT-11, [RSX-11](https://bliptext.com/articles/rsx-11), [TECO](https://bliptext.com/articles/teco-text-editor) and third party ****RTS****s) all ran as user mode processes, independent of the RSTS kernel.\nA [systems manager](https://bliptext.com/articles/system-administrator) could now decide during the bootstrap phase which **RTS** to run as the systems default Keyboard Monitor (**[KBM](https://bliptext.com/articles/command-line-interpreter))**.\nBy now, there were some 3,100 licensed systems.\nIn 1978, the final memory management update was included for all machines that could support 22-bit addressing.\nRSTS could now use the maximum amount of memory available to a PDP-11 (4 megabytes).\nSupport was also included for SUPERVISORY mode which made RSTS the first DEC operating system with this capability.\n[DECnet](https://bliptext.com/articles/decnet) was also supported as well as remote diagnostics from field service technicians at the **RDC** in [Colorado Springs, Colorado](https://bliptext.com/articles/colorado-springs-colorado) (a DEC subscription service).\nBy the end of the [decade](https://bliptext.com/articles/decade), there are over 5,000 licensed systems.\n\n## 1980s\nIn 1981, support for separate instruction and data space for users with [Unibus](https://bliptext.com/articles/unibus) machines ([PDP-11/44](https://bliptext.com/articles/pdp-11-44), PDP-11/45, PDP-11/55 and PDP-11/70) provided an extension to the memory constraints of an individual program.\nCompiling programs to use separate instruction and data space would soon give a program up to 64 KB for instructions, and up to 64 KB for buffering data.\nThe **[DCL](https://bliptext.com/articles/digital-command-language)** RTS was included as well as support for the newer revision of DECnet III.\nBy 1983, with an estimated 15,000 DEC machines running RSTS/E, V8.0-06 included support for the smallest 18-bit PDP-11 sold by DEC (the MicroPDP-11).\nA pre-generated kernel and **CUSPS** were included in this distribution to make installation on the MicroPDP-11 easier.\nDEC sold the pre-generated version on the MicroPDP-11 as MicroRSTS at a reduced price, however users needed to purchase the full version if they had a need to generate their own kernel.\nThe file system was upgraded and given the designation RSTS Directory Structure 1 (RDS1).\nAll previous versions of the RSTS file system are given the designation RDS0.\nThe newer file system was designed to support more than 1700 user accounts.\n\"It is now thought that there are well over 10,000 licensed users and at least an equal number of unlicensed users!\".\nFrom 1985 to 1989, RSTS became a mature product in the [Version 9](https://bliptext.com/articles/) revisions.\n**DCL** was installed as the primary **RTS** and the file system was again upgraded (now RDS1.2) to support new user account features.\nPasswords were encrypted using a modified DES [algorithm](https://bliptext.com/articles/algorithm) instead of limited to six (6) characters stored in [DEC Radix-50](https://bliptext.com/articles/dec-radix-50) format.\nBefore Version 9, there was a non-user system account in the project (group) zero (the designation is [0,1]), and all accounts in project number 1 were privileged (not unlike the [root account](https://bliptext.com/articles/root-account) on [Unix](https://bliptext.com/articles/unix) systems).\nWith the release of Version 9, additional accounts could be created for project zero, and multiple privileges could be individually set for any account.\nSupport for the **[LAT](https://bliptext.com/articles/local-area-transport)** protocol was included, as well as the ability to run the newest version of DECnet IV.\nThese network enhancements give any user connected to a terminal through a [DECserver](https://bliptext.com/articles/decserver) the ability to communicate with a RSTS machine, just as easily as with a [VAX](https://bliptext.com/articles/vax) running [VMS](https://bliptext.com/articles/openvms).\nThe **DCL** command structure between DEC operating systems also contributed to the familiar look and feel:\n\"This is not just another pseudo command file processor; it is based on VMS features. The DCL command file processor is fully supported and integrated in RSTS through extensive changes to DCL and the monitor. DCL executes command files as part of your job; therefore, no pseudo keyboard or forcing of commands to your keyboard is necessary (as with ATPK).\"\n\n## 1990s\nIn 1994, DEC sold most of its PDP-11 software business to [Mentec](https://bliptext.com/articles/mentec-international-ltd).\nDigital continued to support its own PDP-11 customers for a short period after with the assistance of Mentec staff.\nIn 1997, Digital and Mentec granted anyone wishing to use RSTS 9.6 or earlier for non-commercial, hobby purposes no-cost license.\nThe license is only valid on the [SIMH](https://bliptext.com/articles/simh) PDP-11 emulator.\nThe license also covers some other Digital operating systems.\nCopies of the license are included in an authorized software kit available for download on the official website of the [SIMH](https://bliptext.com/articles/simh) emulator.\n\n# Documentation\nThe standard complement of documentation manuals that accompanies a RSTS distribution consists of at least 11 large three-ring binders (collectively known as \"The orange wall\"), one small three-ring binder containing the RSTS/E Quick Reference Guide and a paperback copy of Introduction to BASIC AA-0155B-TK.\nEach of the 11 three-ring binders contains:\nVolume 1: General Information and Installation\nVolume 2: System Management\nVolume 3: System Usage\nVolume 4: Utilities\nVolume 4A: Utilities\nVolume 4B: Utilities\nVolume 5: BASIC-PLUS\nVolume 6: System Programming\nVolume 7: MACRO Programming\nVolume 7A: MACRO Programming\nVolume 8: RMS [ [Record Management Services](https://bliptext.com/articles/record-management-services)]\n# [Example of a RSTS/E document shelf | upload.wikimedia.org/wikipedia/commons/3/37/RSTS///Docs.jpg]\n\n# Operation\n\n## Communication\nRSTS uses a [serial communication](https://bliptext.com/articles/serial-communication) connection to interact with the operator.\nThe connection might be a local [computer terminal](https://bliptext.com/articles/computer-terminal) with a 20 [mA](https://bliptext.com/articles/ampere) [current loop](https://bliptext.com/articles/current-loop) interface, an [RS-232](https://bliptext.com/articles/rs-232) interface (either local [serial port](https://bliptext.com/articles/serial-port) or remote connection via [modem](https://bliptext.com/articles/modem)), or by an [Ethernet](https://bliptext.com/articles/ethernet) connection using DECnet or LAT. As many as 128 terminals (using multi-terminal service) can connect to a RSTS system, running a maximum of 63 jobs (depending on the [processor](https://bliptext.com/articles/central-processing-unit) being used, the amount of memory and disk space, and the [system load](https://bliptext.com/articles/system-load)).\nMost RSTS systems had far fewer terminals.\nUsers can also submit jobs to be run in [batch](https://bliptext.com/articles/batch-file) mode.\nThere is also a batch program called \"ATPK\" that allows users to run a series of commands on an imaginary terminal (pseudo-terminal) in semi-interactive mode similar to batch commands in [MS-DOS](https://bliptext.com/articles/ms-dos).\n\n## Login [Project, Programmer]\nUsers connect to the system by typing the [LOGIN](https://bliptext.com/articles/login) command (or HELLO) at a logged-out terminal and pressing return.\nTyping any command at a logged-out terminal starts the LOGIN program which then interprets the command.\nIf it is one of the commands which were allowed to be used by a user that is not yet logged in (\"Logged Out\"), then the associated program for that command is CHAINed, otherwise the message \"Please say HELLO\" is printed on the terminal.\nPrior to Version 9, a user can also initiate a 1 line login, however this leaves the user's password on the screen for anyone else in the room to view (examples follow):\nBye\nHELLO 1,1;SECRET\nReady\nor\nI 1,1;SECRET\nReady\nor\nLOGIN 1,1;SECRET\nReady\nThe status of a terminal can be determined from the command responses, printed by the command interpreter.\nA logged-in user communicating with the BASIC-PLUS **KBM** (key board monitor) is given the prompt \"Ready\" and a user who is logged out is given the prompt \"Bye\".\nA user logs in by supplying their **PPN** number and password.\nUser numbers consist of a project number (equivalent to a [group number](https://bliptext.com/articles/group-computing) in Unix), a comma, and a programmer number.\nBoth numbers are in the range of 0 to 254, with special exceptions.\nWhen specifying an account, the project and programmer number are enclosed in brackets.\nA typical user number can be [10,5] (project 10, programmer 5), [2,146], [254,31], or [200,220], etc. When a user is running a system program while logged out (because the system manager has enabled it) their **PPN** number is [0,0], and appears in the SYSTAT **CUSP** as **,**.\nThus that is not a valid account number.\nIf the user specifies a slash (/) instead of a comma between the project number and programmer number, a system wide message stored in [1,2]NOTICE.TXT (equivalent to the Unix [motd](https://bliptext.com/articles/message-of-the-day)) will not be displayed at login.\n# [RSTS/E login and logout with BASIC as default RTS | upload.wikimedia.org/wikipedia/commons/e/e2/rsts.png]\n\n## System and user accounts\nIn every project, the programmer number 0 is usually reserved to as a group account, as it can be referenced by the special symbol #.\nIf one's user number is [20,103], a reference to a file name beginning with \"#\" refers to a file stored in the account of the user number [20,0].\nThis feature is useful in educational environments, as programmer number 0 can be issued to the instructor of a class, and the individual students given accounts with the same project number, and the instructor can store in his account files marked as shared only for that project number (which would be students in that class only, and no other).\nTwo special classes of project numbers exist.\nThe project number 0 is generally reserved for system software, and prior to Version 9 there is only 1 project 0 account (named [0,1]).\nProgrammers in the project number 1 are privileged accounts, equivalent to the single account \"root\" on Unix systems, except that the account numbers [1,0] through [1,254] are all privileged accounts.\nAs of Version 9, any account can be granted specific privileges by the systems manager.\nThe account [0,1] is used to store the operating system file itself, all run-time [library](https://bliptext.com/articles/library-computing) systems, and certain system files relating to booting the system (author's comments appear on the right in bold):\nDIR [0,1]\nName .Ext Size Prot Date SY:[0,1]\nBADB .SYS 0P < 63> 06-Jun-98 **List of bad blocks**\nSATT .SYS 3CP < 63> 06-Jun-98 **Bitmap of allocated disk storage**\nINIT .SYS 419P < 40> 06-Jun-98 **[Operating system loader program](https://bliptext.com/articles/boot-loader)**\nERR .ERR 16CP < 40> 06-Jun-98 **System error messages**\nRSTS .SIL 307CP < 60> 06-Jun-98 **Operating system itself**\nBASIC .RTS 73CP < 60> 06-Jun-98 **BASIC-PLUS run time system**\nRT11 .RTS 20C < 60> 06-Jun-98 **RT-11 run time system**\nSWAP .SYS 1024CP < 63> 06-Jun-98 **System [swap file](https://bliptext.com/articles/swap-file)**\nCRASH .SYS 35CP < 63> 06-Jun-98 **[System crash dump](https://bliptext.com/articles/core-dump)**\nRSX .RTS 16C < 60> 23-Sep-79 **RSX-11 run-time system**\nTECO .RTS 39C < 60> 24-Sep-79 **TECO text editor**\nTotal of 1952 blocks in 11 files in SY:[0,1]\n(Editor's note: This directory listing is prior to Version 9.)\nThe **DIR** command is an installed CCL equivalent to a RUN command for the **DIR**ECT program.\n[0,1] is the account number (and directory name) of the operating system storage account.\nIt would be referred to as \"project number 0, programmer number 1\".\nThe numbers shown after each file represent its size in disk blocks, a block being 512 [bytes](https://bliptext.com/articles/byte) or 1/2 kilobyte (K).\n\"C\" indicates the file is contiguous (is stored as one file without being separated into pieces, similar to files on a [Microsoft Windows](https://bliptext.com/articles/microsoft-windows) system after a drive has been [defragmented](https://bliptext.com/articles/defragmentation)), while \"P\" indicates it is specially protected (cannot be deleted, even by a privileged user, unless the P bit is cleared by separate command).\nThe numbers in brackets (like \"< 40>\") represent the protections for the file, which is always displayed in decimal.\nProtections indicate if the file may be seen by any other user, by other users with the same programmer number, if the file is read only or if it may be altered by another user, and whether the file may be executed by an ordinary user giving them additional privileges.\nThese protection codes are very similar to the [r, w and x protections](https://bliptext.com/articles/file-system-permissions) in [Unix](https://bliptext.com/articles/unix) and similar operating systems such as [BSD](https://bliptext.com/articles/bsd) and [Linux](https://bliptext.com/articles/linux).\nCode 60 is equivalent to a private file, code 63 is a private non-deletable file, and 40 is a public file.\nLibrary files are kept in account [1,1] and it is usually referenced by the logical name LB:.\nThe account [1,2] is the system startup account (much like a Unix system starting up under root), and contains the system ****CUSP**S** that could be referenced by prefixing the **CUSP** name with a dollar sign ($).\n\"!\" is used for account [1,3], \"%\" for [1,4] and \"&\" for [1,5].\nThe account [1,1] also had the special privilege of being the only account where a user logged in under that account is permitted to execute the [POKE](https://bliptext.com/articles/peek-and-poke) system call to put values into any memory in the system.\nThus the account number [1,1] is the closest equivalent to \"root\" on Unix-based systems.\n\n# Run-time environments\nOne of the features of RSTS is the means for the execution of programs and the environment used to run them.\nThe various environments allowed for programming in BASIC-PLUS, the enhanced and hard compiled BASIC-Plus-2, and in more traditional programming languages such as [COBOL](https://bliptext.com/articles/cobol) (eventually upgraded to [COBOL](https://bliptext.com/articles/cobol)-85) and [FORTRAN](https://bliptext.com/articles/fortran) IV (eventually upgraded to [FORTRAN](https://bliptext.com/articles/fortran)-77).\nOther languages were supported such as [DIBOL](https://bliptext.com/articles/dibol) and [MUMPS](https://bliptext.com/articles/mumps).\nThese environments were separate from each other such that one could start a program from one environment and the system would switch to a different environment while running a different program, and then return the user to the original environment they started with.\nThese environments were referred to as a Runtime System (RTS).\nThe term for the [command line interface](https://bliptext.com/articles/command-line-interface) that most of these RTSs had was the KBM.\nPrior to Version 9, the systems manager needed to define which RTS the system would start under, and it had to be one that would execute compiled programs.\nA systems manager may also install special **CCL** (concise command language) commands, which take precedence over all KBM commands (with the exception of **DCL**).\nA CCL is analogous to a shortcut to a program on a Windows system or a [symbolic link](https://bliptext.com/articles/symbolic-link) on Unix-based systems.\nCCLs are installed as a [memory-resident](https://bliptext.com/articles/memory-resident) command either during startup, or dynamically while the system is running by a system's manager (i.e.: it is not permanent like a disk file).\nWhen logged in, a user can \"SWITCH\" to any of these environments, type language statements in the BASIC-PLUS programming language, issue RUN commands to specific programs, or issue a special command called a **CCL** to execute a program with command options.\nMost RSTS systems managers generated the kernel to include the \"Control-T\" one line status option which could tell the user what program they were running, under what ****RTS**** the program was using, how much memory the program was taking, how much it could expand to, and how much memory the ****RTS**** was using.\n\n## BASIC-PLUS\nPrograms written in [BASIC-PLUS](https://bliptext.com/articles/basic-plus) ran under the BASIC **RTS**, which allowed them up to 32K bytes of memory (out of 64K total).\nThe language was interpreted, each different keyword being internally converted to a unique [byte code](https://bliptext.com/articles/byte-code) and the variables and data being indexed and stored separately within the memory space.\nThe internal byte-code format was known as PCODE.\nWhen the interactive SAVE command was issued, the BASIC Plus **RTS** simply saved the working memory area to a disk file with a \".BAC\" extension.\nAlthough this format was undocumented, two Electronic Engineering undergraduates from [Southampton University](https://bliptext.com/articles/southampton-university) in the UK (Nick de Smith and David Garrod) developed a [decompiler](https://bliptext.com/articles/decompiler) that could [reverse engineer](https://bliptext.com/articles/reverse-engineer) BAC files into their original BASIC-Plus source, complete with original line numbers and variable names (both subsequently worked for DEC).\nThe rest of the memory was used by the BASIC **RTS** itself.\nIf one wrote programs in a language that permitted true binary executables such as BASIC-Plus-2, FORTRAN-IV, or Macro Assembler, then the amount of memory available would be 56K (8K allocated to the **RTS**).\nThe standard BASIC-PLUS prompt is the \"Ready\" response, pressing [Control-T displays status](https://bliptext.com/articles/status-key) (example):\nnew\nNew file name--HWORLD\nReady\nHWORLD 10:17 PM 01-Jan-08\nHello World\nPress Control-T for 1 line status: ?\n1 KB0 HWORLD+BASIC KB(0R) 2(16)K+14K 0.2(+0.0) +0\nReady\nsave\nReady\ncompile\nReady\nSY:[1,2]\nHWORLD.BAS 1 < 60>\nHWORLD.BAC 7C\nTotal of 8 blocks in 2 files in SY:[1,2]\nReady\n\n## DCL (Digital Command Language)\nStarting with Version 9, **DCL** became the primary startup **RTS** even though it does not have the ability to execute binary programs.\nThis became possible with the advent of the disappearing RSX **RTS** (see below).\n**DCL** was incorporated into all of the recent versions of DEC's operating systems (RSX-11, RT-11, [VMS](https://bliptext.com/articles/openvms), and later Open[VMS](https://bliptext.com/articles/openvms)) for compatibility.\nThe standard **DCL** prompt is the dollar \"$\" sign (example):\n\n## RSX (Realtime System eXecutive)\nPrograms that were written for the RSX ****RTS**** such as COBOL, Macro Assembler, or later releases of BASIC-Plus-2, could use the maximum amount of memory available for a binary program (56K due to the requirements of an ****RTS**** needing the top 8K to use for itself).\nRSTS Version 7 and later allowed the RSX **RTS** to be included in the kernel, making it completely \"disappear\" from the user address space, thus allowing 64K bytes of memory for user programs.\nPrograms got around the limitations of the amount of available memory by using libraries (when permissible), by complicated overlay strategies, or by calling other programs (\"Chaining\") and passing them commands and data in a shared memory area called \"Core Common,\" among other practices.\nWhen RSX is the default **KBM**, the standard RSX prompt (both logged in and logged out) is the \">\" (or MCR \"Monitor Console Routine\") sign (example):\n\n## RT-11\nThe RT-11 **RTS** emulated the Single Job version of the RT-11 distribution.\nLike the RSX emulation, RT-11 occupied the top 8K of memory, leaving the bottom 56K for **CUSPS**, programs written in FORTRAN-IV or Macro Assembler.\nWhen RT-11 is the default **KBM**, the standard RT-11 prompt (both logged in and logged out) is the \".\"\nsign (example):\n\n## TECO (Text Editor and COrrector)\nThe [TECO editor](https://bliptext.com/articles/teco-text-editor) was itself implemented as an RTS to maximize the amount of memory available for the editing buffer, and also because it was first implemented in RSTS V5B, before the release of the general purpose runtime systems (RSX and RT11).\nTECO was the only RTS distributed with RSTS that did not contain a built-in KBM.\nThe user would start up TECO (like any other program) by running a TECO program (TECO.TEC).\nTECO and the affine QEDIT were the direct ancestors of the first UNIX-based text editor, ED.\nMost RSTS systems used CCL's to create a file (MAKE filespec), edit a file (TECO filespec), or run a TECO program (MUNG filespec, data).\nThe following program is an example of how TECO could be used to calculate [pi](https://bliptext.com/articles/pi) (currently set to 20 digits):\n\n# RSTS easter eggs\n\n## System start-up (INIT.SYS)\nIf a user typed an unrecognized command at system boot to the \"Option:\" prompt of INIT.SYS, the startup utility, the message \"Type 'HELP' for help\" was displayed.\nIf the user subsequently typed 'HELP' (including the quotes) to the prompt, the response was \"How amusing, anyway...\"\nfollowed by the actual help message.\n\n## PDP-11 console lights\nA system manager could compile into the kernel a rotating display pattern that gave the illusion of two snakes chasing each other around the console lights.\nThe normal kernel would give the illusion of one snake moving from right to left in the data lights across the bottom.\nIf the system manager also compiled the \"lights\" object module the user would see an additional snake moving from left to right in the address lights across the top.\nThis was accomplished by using supervisory mode in the versions prior to 9.0.\nRSX also had a similar display pattern that would appear as if two snakes were playing chicken and would run into each other in the center of the console.\n\n## Teco easter egg\nThe command 'make' allowed a user to make a text file and automatically enter the TECO text editor.\nIf a user typed 'make love', the system created a file called 'love' and typed back, 'Not War?'\n\n## Open Files List\nKevin Herbert, later working for DEC, added an undocumented feature in the 90's to allow a user to enter ^F to see a list of open files the user process had, complete with blocks in use and file sizes.\n\n## Stardate\nBeginning with version 9.0, an [undocumented feature](https://bliptext.com/articles/undocumented-feature) would allow the system manager to change the display of the system date.\nRSTS became the first operating system that would display the system date as a set of numbers representing a [stardate](https://bliptext.com/articles/stardate) as commonly known from the TV series Star Trek.\n\n# Add-ons by other companies\n[System Industries](https://bliptext.com/articles/system-industries) bought the only source license for RSTS to implement an enhancement called (SImultaneous Machine ACceSs), which allowed their special disk controller to set a semaphore flag for disk access, allowing multiple WRITES to the same files on a RSTS System where the disk is shared by multiple PDP-11 RSTS systems.\nThis feature was implemented in System Industries controllers that were attached to many DEC computers and designed by Dr. Albert Chu while he worked at System Industries.\nThe main innovation was use of a [semaphore](https://bliptext.com/articles/semaphore-programming), a flag to indicate which processor, by cooperative sharing, has exclusive write access.\nThis required many changes to the way access to disks was accomplished by the RSTS operating system.\nThe FIPS (File Information Processing System) system, that handled i/o access, was single-threaded in RSTS.\nTo allow a disk access to stall while another machine had active access to a block, required that the FIPS could timeout a request, go to the next request and 'come back' to the stalled one in a [round robin](https://bliptext.com/articles/round-robin-scheduling) fashion.\nThe code to allow this was written by Philip Hunt while working at System Industries, in [Milpitas, California](https://bliptext.com/articles/milpitas-california).\nHe eventually worked for Digital Equipment in the New England area in the late 1980s and early 1990s.\nSIMACS was not limited to the PDP-11 product line; VAXen could also use it.\n\n# RSTS emulations\n\n## ROSS/V\nIn 1981, Evans Griffiths & Hart marketed the ROSS/V product.\nROSS/V allowed all user mode processes of RSTS (**CUSPS**, **RTS**s and user programs) the ability to run unmodified under VMS on the VAX-11 machines.\nThe code for this emulation handled all of the kernel processes that would normally be handled by a RSTS kernel running on a PDP-11.\nThe original BASIC-PLUS language that has carried through all versions of RSTS was subcontracted by Evans Griffiths & Hart, Inc. for a fixed price of $10,500.\n\n## Other PDP-11 emulators\nRSTS and its applications can run under a number of PDP-11 emulators such as [SIMH](https://bliptext.com/articles/simh) and [Ersatz-11](https://bliptext.com/articles/pdp-11).\nFor more information, see [PDP-11](https://bliptext.com/articles/pdp-11).\n\n# RSTS mascot\n\n## Spike and Albert\n\n# Versions\nRSTS was originally called BTSS (Basic Time Sharing System).\nBefore shipment began, the name was changed from BTSS to RTSS because a product called BTSS was already being marketed by [Honeywell](https://bliptext.com/articles/honeywell).\nA simple typing mistake changed the name from RTSS to RSTS.\nThe addition of new memory management support and the ability to install more memory in the PDP-11/40 and PDP-11/45 led to another name change: RSTS-11 now became RSTS/E.\n\n## Clones in the USSR\n\n# Applications\nComputer [bureaus](https://bliptext.com/articles/service-bureau) sometimes deployed User-11 for RSTS/E-based [data management](https://bliptext.com/articles/data-management).","current_revision":null,"created_by":"kACnuQmH5k9Nr5VNVEpVeg7XpvUmMctD","created_at":"2025-01-25T19:08:16.574Z","updated_at":"2025-01-25T19:08:16.574Z","search_vector":"'rsts/e':1","search_content":" \n \n**Name:** RSTS \n**Screenshot:** Rstse-10 1.png \n**Developer:** [Digital Equipment Corporation](https://bliptext.com/articles/digital-equipment-corporation), later [Mentec](https://bliptext.com/articles/mentec-international-ltd) \n**Source Model:** [Closed source](https://bliptext.com/articles/closed-source) \n**Kernel Type:** [Time-sharing](https://bliptext.com/articles/time-sharing) [operating systems](https://bliptext.com/articles/operating-system) \n**Supported Platforms:** [PDP-11](https://bliptext.com/articles/pdp-11) \n**Ui:** [Command-line interface](https://bliptext.com/articles/command-line-interface): [DCL (Digital Command Language)](https://bliptext.com/articles/digital-command-language) \n**Released:** 1970 \n**Latest Release Version:** RSTS V10.1 \n**Latest Release Date:** 1992 \n**Language:** [English](https://bliptext.com/articles/english-language) \n**Programmed In:** [MACRO-11](https://bliptext.com/articles/macro-11) [assembly language](https://bliptext.com/articles/assembly-language), [BASIC-PLUS](https://bliptext.com/articles/basic-plus)-2, [DCL](https://bliptext.com/articles/digital-command-language) \n**Prog Language:** [ALGOL-60](https://bliptext.com/articles/algol), [APL](https://bliptext.com/articles/apl-programming-language), [BASI[C](https://bliptext.com/articles/c-programming-language)-PLUS](https://bliptext.com/articles/basic-plus), [BASI[C](https://bliptext.com/articles/c-programming-language)-PLUS](https://bliptext.com/articles/basic-plus)-2, [C](https://bliptext.com/articles/c-programming-language), [C](https://bliptext.com/articles/c-programming-language)OBOL, [DATATRIEVE](https://bliptext.com/articles/datatrieve), [DIBOL](https://bliptext.com/articles/dibol), [Forth](https://bliptext.com/articles/forth-programming-language), [Fortran](https://bliptext.com/articles/fortran), MA[C](https://bliptext.com/articles/c-programming-language)RO-11, [Pascal](https://bliptext.com/articles/pascal-programming-language), [RPG II](https://bliptext.com/articles/ibm-rpg), TE[C](https://bliptext.com/articles/c-programming-language)O \n**Updatemodel:** Binary patches, complete binaries \n**Package Manager:** BACKUP \n**Working State:** No development, still available \n**License:** [Proprietary](https://bliptext.com/articles/proprietary-software) \n**Preceded By:** [TSS/8](https://bliptext.com/articles/tss-8) \n \n\n# \n**RSTS** is a [multi-user](https://bliptext.com/articles/multi-user) [time-sharing](https://bliptext.com/articles/time-sharing) [operating system](https://bliptext.com/articles/operating-system) developed by [Digital Equipment Corporation](https://bliptext.com/articles/digital-equipment-corporation) (DEC, now part of [Hewlett-Packard](https://bliptext.com/articles/hewlett-packard)) for the [PDP-11](https://bliptext.com/articles/pdp-11) series of [16-bit](https://bliptext.com/articles/16-bit) [minicomputers](https://bliptext.com/articles/minicomputer).\nThe first version of RSTS (RSTS-11, [Version 1](https://bliptext.com/articles/)) was implemented in 1970 by DEC [software engineers](https://bliptext.com/articles/software-engineering) that developed the [TSS-8](https://bliptext.com/articles/tss-8) time-sharing operating system for the [PDP-8](https://bliptext.com/articles/pdp-8).\nThe last version of RSTS (RSTS/E, [Version 10.1](https://bliptext.com/articles/)) was released in September 1992.\nRSTS-11 and RSTS/E are usually referred to just as \"RSTS\" and this article will generally use the shorter form.\nRSTS-11 supports the BASIC programming language, an extended version called BASIC-PLUS, developed under contract by Evans Griffiths & Hart of Boston.\nStarting with RSTS/E version 5B, DEC added support for additional programming languages by emulating the execution environment of the [RT-11](https://bliptext.com/articles/rt-11) and [RSX-11](https://bliptext.com/articles/rsx-11) operating systems.\n\n# Acronyms and abbreviations\n\n# Development\n\n## 1970s\nThe [kernel](https://bliptext.com/articles/kernel-operating-system) of RSTS was [[program](https://bliptext.com/articles/computer-program)med](https://bliptext.com/articles/computer-[program](https://bliptext.com/articles/computer-program)ming) in the [assembly language](https://bliptext.com/articles/assembly-language) [MACRO-11](https://bliptext.com/articles/macro-11), [compiled](https://bliptext.com/articles/compiler) and [installed](https://bliptext.com/articles/installation-computer-[program](https://bliptext.com/articles/computer-program)s) to a [disk](https://bliptext.com/articles/hard-disk-drive) using the **[CILUS](https://bliptext.com/articles/dos-11)** [program](https://bliptext.com/articles/computer-program), running on a [DOS-11](https://bliptext.com/articles/dos-11) operating system.\nRSTS [booted](https://bliptext.com/articles/booting) into an extended version of the [BASIC](https://bliptext.com/articles/basic) programming language which DEC called \"[BASIC](https://bliptext.com/articles/basic)-PLUS\".\nAll of the [system software](https://bliptext.com/articles/system-software) **CUSPS** for the operating system, including the programs for resource accounting, [login](https://bliptext.com/articles/login), logout, and managing the system, were written in BASIC-PLUS.\nFrom 1970 to 1973, RSTS ran in only [56K bytes](https://bliptext.com/articles/kilobyte) of [magnetic core memory](https://bliptext.com/articles/magnetic-core-memory) (64 kilobytes including the [memory-mapped I/O](https://bliptext.com/articles/memory-mapped-i-o) space).\nThis would allow a system to have up to 16 [terminals](https://bliptext.com/articles/computer-terminal) with a maximum of 17 [jobs](https://bliptext.com/articles/job-computing).\nThe maximum program size was 16K bytes.\nBy the end of 1973 DEC estimated there were 150 [licensed](https://bliptext.com/articles/license) systems running RSTS.\nIn 1973, [memory management](https://bliptext.com/articles/memory-management) support was included in RSTS (now RSTS/E) for the newer DEC [PDP-11/40](https://bliptext.com/articles/pdp-11-40) and [PDP-11/45](https://bliptext.com/articles/pdp-11-45) minicomputers (the [PDP-11/20](https://bliptext.com/articles/pdp-11-20) was only supported under RSTS-11).\nThe introduction of memory management in the newer PDP-11 computers not only meant these machines were able to address four times the amount of memory (18-bit [addressing](https://bliptext.com/articles/addressing), 256K bytes), it also paved the way for the developers to separate [user mode](https://bliptext.com/articles/user-space) processes from the core of the kernel.\nIn 1975, memory management support was again updated for the newer 22-bit addressable [PDP-11/70](https://bliptext.com/articles/pdp-11-70).\nRSTS systems could now be expanded to use as much as two [megabytes](https://bliptext.com/articles/megabyte) of memory running up to 63 jobs.\nThe **[RTS](https://bliptext.com/articles/run-time-system)** and **[CCL](https://bliptext.com/articles/concise-command-language)** concepts were introduced although they had to be compiled in during \"[SYSGEN](https://bliptext.com/articles/system-generation)\".\nMulti-terminal service was introduced which would allow a single job the ability to control multiple terminals (128 total).\nLarge-message send/receive and interprocess communication became very sophisticated and efficient.\nBy August there are 1,200 licensed systems.\nIn 1977, the installation process for RSTS was no longer dependent on DOS-11.\nThe RSTS kernel could now be compiled under the [RT-11](https://bliptext.com/articles/rt-11) **RTS**, formatted as a kernel file with [RT-11](https://bliptext.com/articles/rt-11) **SILUS**, and [copied](https://bliptext.com/articles/copying) to the system or other disks, while the [computer](https://bliptext.com/articles/computer) was time-sharing.\nThe BASIC-PLUS ****RTS**** (as well as RT-11, [RSX-11](https://bliptext.com/articles/rsx-11), [TECO](https://bliptext.com/articles/teco-text-editor) and third party ****RTS****s) all ran as user mode processes, independent of the RSTS kernel.\nA [systems manager](https://bliptext.com/articles/system-administrator) could now decide during the bootstrap phase which **RTS** to run as the systems default Keyboard Monitor (**[KBM](https://bliptext.com/articles/command-line-interpreter))**.\nBy now, there were some 3,100 licensed systems.\nIn 1978, the final memory management update was included for all machines that could support 22-bit addressing.\nRSTS could now use the maximum amount of memory available to a PDP-11 (4 megabytes).\nSupport was also included for SUPERVISORY mode which made RSTS the first DEC operating system with this capability.\n[DECnet](https://bliptext.com/articles/decnet) was also supported as well as remote diagnostics from field service technicians at the **RDC** in [Colorado Springs, Colorado](https://bliptext.com/articles/colorado-springs-colorado) (a DEC subscription service).\nBy the end of the [decade](https://bliptext.com/articles/decade), there are over 5,000 licensed systems.\n\n## 1980s\nIn 1981, support for separate instruction and data space for users with [Unibus](https://bliptext.com/articles/unibus) machines ([PDP-11/44](https://bliptext.com/articles/pdp-11-44), PDP-11/45, PDP-11/55 and PDP-11/70) provided an extension to the memory constraints of an individual program.\nCompiling programs to use separate instruction and data space would soon give a program up to 64 KB for instructions, and up to 64 KB for buffering data.\nThe **[DCL](https://bliptext.com/articles/digital-command-language)** RTS was included as well as support for the newer revision of DECnet III.\nBy 1983, with an estimated 15,000 DEC machines running RSTS/E, V8.0-06 included support for the smallest 18-bit PDP-11 sold by DEC (the MicroPDP-11).\nA pre-generated kernel and **CUSPS** were included in this distribution to make installation on the MicroPDP-11 easier.\nDEC sold the pre-generated version on the MicroPDP-11 as MicroRSTS at a reduced price, however users needed to purchase the full version if they had a need to generate their own kernel.\nThe file system was upgraded and given the designation RSTS Directory Structure 1 (RDS1).\nAll previous versions of the RSTS file system are given the designation RDS0.\nThe newer file system was designed to support more than 1700 user accounts.\n\"It is now thought that there are well over 10,000 licensed users and at least an equal number of unlicensed users!\".\nFrom 1985 to 1989, RSTS became a mature product in the [Version 9](https://bliptext.com/articles/) revisions.\n**DCL** was installed as the primary **RTS** and the file system was again upgraded (now RDS1.2) to support new user account features.\nPasswords were encrypted using a modified DES [algorithm](https://bliptext.com/articles/algorithm) instead of limited to six (6) characters stored in [DEC Radix-50](https://bliptext.com/articles/dec-radix-50) format.\nBefore Version 9, there was a non-user system account in the project (group) zero (the designation is [0,1]), and all accounts in project number 1 were privileged (not unlike the [root account](https://bliptext.com/articles/root-account) on [Unix](https://bliptext.com/articles/unix) systems).\nWith the release of Version 9, additional accounts could be created for project zero, and multiple privileges could be individually set for any account.\nSupport for the **[LAT](https://bliptext.com/articles/local-area-transport)** protocol was included, as well as the ability to run the newest version of DECnet IV.\nThese network enhancements give any user connected to a terminal through a [DECserver](https://bliptext.com/articles/decserver) the ability to communicate with a RSTS machine, just as easily as with a [VAX](https://bliptext.com/articles/vax) running [VMS](https://bliptext.com/articles/openvms).\nThe **DCL** command structure between DEC operating systems also contributed to the familiar look and feel:\n\"This is not just another pseudo command file processor; it is based on VMS features. The DCL command file processor is fully supported and integrated in RSTS through extensive changes to DCL and the monitor. DCL executes command files as part of your job; therefore, no pseudo keyboard or forcing of commands to your keyboard is necessary (as with ATPK).\"\n\n## 1990s\nIn 1994, DEC sold most of its PDP-11 software business to [Mentec](https://bliptext.com/articles/mentec-international-ltd).\nDigital continued to support its own PDP-11 customers for a short period after with the assistance of Mentec staff.\nIn 1997, Digital and Mentec granted anyone wishing to use RSTS 9.6 or earlier for non-commercial, hobby purposes no-cost license.\nThe license is only valid on the [SIMH](https://bliptext.com/articles/simh) PDP-11 emulator.\nThe license also covers some other Digital operating systems.\nCopies of the license are included in an authorized software kit available for download on the official website of the [SIMH](https://bliptext.com/articles/simh) emulator.\n\n# Documentation\nThe standard complement of documentation manuals that accompanies a RSTS distribution consists of at least 11 large three-ring binders (collectively known as \"The orange wall\"), one small three-ring binder containing the RSTS/E Quick Reference Guide and a paperback copy of Introduction to BASIC AA-0155B-TK.\nEach of the 11 three-ring binders contains:\nVolume 1: General Information and Installation\nVolume 2: System Management\nVolume 3: System Usage\nVolume 4: Utilities\nVolume 4A: Utilities\nVolume 4B: Utilities\nVolume 5: BASIC-PLUS\nVolume 6: System Programming\nVolume 7: MACRO Programming\nVolume 7A: MACRO Programming\nVolume 8: RMS [ [Record Management Services](https://bliptext.com/articles/record-management-services)]\n# [Example of a RSTS/E document shelf | upload.wikimedia.org/wikipedia/commons/3/37/RSTS///Docs.jpg]\n\n# Operation\n\n## Communication\nRSTS uses a [serial communication](https://bliptext.com/articles/serial-communication) connection to interact with the operator.\nThe connection might be a local [computer terminal](https://bliptext.com/articles/computer-terminal) with a 20 [mA](https://bliptext.com/articles/ampere) [current loop](https://bliptext.com/articles/current-loop) interface, an [RS-232](https://bliptext.com/articles/rs-232) interface (either local [serial port](https://bliptext.com/articles/serial-port) or remote connection via [modem](https://bliptext.com/articles/modem)), or by an [Ethernet](https://bliptext.com/articles/ethernet) connection using DECnet or LAT. As many as 128 terminals (using multi-terminal service) can connect to a RSTS system, running a maximum of 63 jobs (depending on the [processor](https://bliptext.com/articles/central-processing-unit) being used, the amount of memory and disk space, and the [system load](https://bliptext.com/articles/system-load)).\nMost RSTS systems had far fewer terminals.\nUsers can also submit jobs to be run in [batch](https://bliptext.com/articles/batch-file) mode.\nThere is also a batch program called \"ATPK\" that allows users to run a series of commands on an imaginary terminal (pseudo-terminal) in semi-interactive mode similar to batch commands in [MS-DOS](https://bliptext.com/articles/ms-dos).\n\n## Login [Project, Programmer]\nUsers connect to the system by typing the [LOGIN](https://bliptext.com/articles/login) command (or HELLO) at a logged-out terminal and pressing return.\nTyping any command at a logged-out terminal starts the LOGIN program which then interprets the command.\nIf it is one of the commands which were allowed to be used by a user that is not yet logged in (\"Logged Out\"), then the associated program for that command is CHAINed, otherwise the message \"Please say HELLO\" is printed on the terminal.\nPrior to Version 9, a user can also initiate a 1 line login, however this leaves the user's password on the screen for anyone else in the room to view (examples follow):\nBye\nHELLO 1,1;SECRET\nReady\nor\nI 1,1;SECRET\nReady\nor\nLOGIN 1,1;SECRET\nReady\nThe status of a terminal can be determined from the command responses, printed by the command interpreter.\nA logged-in user communicating with the BASIC-PLUS **KBM** (key board monitor) is given the prompt \"Ready\" and a user who is logged out is given the prompt \"Bye\".\nA user logs in by supplying their **PPN** number and password.\nUser numbers consist of a project number (equivalent to a [group number](https://bliptext.com/articles/group-computing) in Unix), a comma, and a programmer number.\nBoth numbers are in the range of 0 to 254, with special exceptions.\nWhen specifying an account, the project and programmer number are enclosed in brackets.\nA typical user number can be [10,5] (project 10, programmer 5), [2,146], [254,31], or [200,220], etc. When a user is running a system program while logged out (because the system manager has enabled it) their **PPN** number is [0,0], and appears in the SYSTAT **CUSP** as **,**.\nThus that is not a valid account number.\nIf the user specifies a slash (/) instead of a comma between the project number and programmer number, a system wide message stored in [1,2]NOTICE.TXT (equivalent to the Unix [motd](https://bliptext.com/articles/message-of-the-day)) will not be displayed at login.\n# [RSTS/E login and logout with BASIC as default RTS | upload.wikimedia.org/wikipedia/commons/e/e2/rsts.png]\n\n## System and user accounts\nIn every project, the programmer number 0 is usually reserved to as a group account, as it can be referenced by the special symbol #.\nIf one's user number is [20,103], a reference to a file name beginning with \"#\" refers to a file stored in the account of the user number [20,0].\nThis feature is useful in educational environments, as programmer number 0 can be issued to the instructor of a class, and the individual students given accounts with the same project number, and the instructor can store in his account files marked as shared only for that project number (which would be students in that class only, and no other).\nTwo special classes of project numbers exist.\nThe project number 0 is generally reserved for system software, and prior to Version 9 there is only 1 project 0 account (named [0,1]).\nProgrammers in the project number 1 are privileged accounts, equivalent to the single account \"root\" on Unix systems, except that the account numbers [1,0] through [1,254] are all privileged accounts.\nAs of Version 9, any account can be granted specific privileges by the systems manager.\nThe account [0,1] is used to store the operating system file itself, all run-time [library](https://bliptext.com/articles/library-computing) systems, and certain system files relating to booting the system (author's comments appear on the right in bold):\nDIR [0,1]\nName .Ext Size Prot Date SY:[0,1]\nBADB .SYS 0P 06-Jun-98 **List of bad blocks**\nSATT .SYS 3CP 06-Jun-98 **Bitmap of allocated disk storage**\nINIT .SYS 419P 06-Jun-98 **[Operating system loader program](https://bliptext.com/articles/boot-loader)**\nERR .ERR 16CP 06-Jun-98 **System error messages**\nRSTS .SIL 307CP 06-Jun-98 **Operating system itself**\nBASIC .RTS 73CP 06-Jun-98 **BASIC-PLUS run time system**\nRT11 .RTS 20C 06-Jun-98 **RT-11 run time system**\nSWAP .SYS 1024CP 06-Jun-98 **System [swap file](https://bliptext.com/articles/swap-file)**\nCRASH .SYS 35CP 06-Jun-98 **[System crash dump](https://bliptext.com/articles/core-dump)**\nRSX .RTS 16C 23-Sep-79 **RSX-11 run-time system**\nTECO .RTS 39C 24-Sep-79 **TECO text editor**\nTotal of 1952 blocks in 11 files in SY:[0,1]\n(Editor's note: This directory listing is prior to Version 9.)\nThe **DIR** command is an installed CCL equivalent to a RUN command for the **DIR**ECT program.\n[0,1] is the account number (and directory name) of the operating system storage account.\nIt would be referred to as \"project number 0, programmer number 1\".\nThe numbers shown after each file represent its size in disk blocks, a block being 512 [bytes](https://bliptext.com/articles/byte) or 1/2 kilobyte (K).\n\"C\" indicates the file is contiguous (is stored as one file without being separated into pieces, similar to files on a [Microsoft Windows](https://bliptext.com/articles/microsoft-windows) system after a drive has been [defragmented](https://bliptext.com/articles/defragmentation)), while \"P\" indicates it is specially protected (cannot be deleted, even by a privileged user, unless the P bit is cleared by separate command).\nThe numbers in brackets (like \" \") represent the protections for the file, which is always displayed in decimal.\nProtections indicate if the file may be seen by any other user, by other users with the same programmer number, if the file is read only or if it may be altered by another user, and whether the file may be executed by an ordinary user giving them additional privileges.\nThese protection codes are very similar to the [r, w and x protections](https://bliptext.com/articles/file-system-permissions) in [Unix](https://bliptext.com/articles/unix) and similar operating systems such as [BSD](https://bliptext.com/articles/bsd) and [Linux](https://bliptext.com/articles/linux).\nCode 60 is equivalent to a private file, code 63 is a private non-deletable file, and 40 is a public file.\nLibrary files are kept in account [1,1] and it is usually referenced by the logical name LB:.\nThe account [1,2] is the system startup account (much like a Unix system starting up under root), and contains the system ****CUSP**S** that could be referenced by prefixing the **CUSP** name with a dollar sign ($).\n\"!\" is used for account [1,3], \"%\" for [1,4] and \"&\" for [1,5].\nThe account [1,1] also had the special privilege of being the only account where a user logged in under that account is permitted to execute the [POKE](https://bliptext.com/articles/peek-and-poke) system call to put values into any memory in the system.\nThus the account number [1,1] is the closest equivalent to \"root\" on Unix-based systems.\n\n# Run-time environments\nOne of the features of RSTS is the means for the execution of programs and the environment used to run them.\nThe various environments allowed for programming in BASIC-PLUS, the enhanced and hard compiled BASIC-Plus-2, and in more traditional programming languages such as [COBOL](https://bliptext.com/articles/cobol) (eventually upgraded to [COBOL](https://bliptext.com/articles/cobol)-85) and [FORTRAN](https://bliptext.com/articles/fortran) IV (eventually upgraded to [FORTRAN](https://bliptext.com/articles/fortran)-77).\nOther languages were supported such as [DIBOL](https://bliptext.com/articles/dibol) and [MUMPS](https://bliptext.com/articles/mumps).\nThese environments were separate from each other such that one could start a program from one environment and the system would switch to a different environment while running a different program, and then return the user to the original environment they started with.\nThese environments were referred to as a Runtime System (RTS).\nThe term for the [command line interface](https://bliptext.com/articles/command-line-interface) that most of these RTSs had was the KBM.\nPrior to Version 9, the systems manager needed to define which RTS the system would start under, and it had to be one that would execute compiled programs.\nA systems manager may also install special **CCL** (concise command language) commands, which take precedence over all KBM commands (with the exception of **DCL**).\nA CCL is analogous to a shortcut to a program on a Windows system or a [symbolic link](https://bliptext.com/articles/symbolic-link) on Unix-based systems.\nCCLs are installed as a [memory-resident](https://bliptext.com/articles/memory-resident) command either during startup, or dynamically while the system is running by a system's manager (i.e.: it is not permanent like a disk file).\nWhen logged in, a user can \"SWITCH\" to any of these environments, type language statements in the BASIC-PLUS programming language, issue RUN commands to specific programs, or issue a special command called a **CCL** to execute a program with command options.\nMost RSTS systems managers generated the kernel to include the \"Control-T\" one line status option which could tell the user what program they were running, under what ****RTS**** the program was using, how much memory the program was taking, how much it could expand to, and how much memory the ****RTS**** was using.\n\n## BASIC-PLUS\nPrograms written in [BASIC-PLUS](https://bliptext.com/articles/basic-plus) ran under the BASIC **RTS**, which allowed them up to 32K bytes of memory (out of 64K total).\nThe language was interpreted, each different keyword being internally converted to a unique [byte code](https://bliptext.com/articles/byte-code) and the variables and data being indexed and stored separately within the memory space.\nThe internal byte-code format was known as PCODE.\nWhen the interactive SAVE command was issued, the BASIC Plus **RTS** simply saved the working memory area to a disk file with a \".BAC\" extension.\nAlthough this format was undocumented, two Electronic Engineering undergraduates from [Southampton University](https://bliptext.com/articles/southampton-university) in the UK (Nick de Smith and David Garrod) developed a [decompiler](https://bliptext.com/articles/decompiler) that could [reverse engineer](https://bliptext.com/articles/reverse-engineer) BAC files into their original BASIC-Plus source, complete with original line numbers and variable names (both subsequently worked for DEC).\nThe rest of the memory was used by the BASIC **RTS** itself.\nIf one wrote programs in a language that permitted true binary executables such as BASIC-Plus-2, FORTRAN-IV, or Macro Assembler, then the amount of memory available would be 56K (8K allocated to the **RTS**).\nThe standard BASIC-PLUS prompt is the \"Ready\" response, pressing [Control-T displays status](https://bliptext.com/articles/status-key) (example):\nnew\nNew file name--HWORLD\nReady\nHWORLD 10:17 PM 01-Jan-08\nHello World\nPress Control-T for 1 line status: ?\n1 KB0 HWORLD+BASIC KB(0R) 2(16)K+14K 0.2(+0.0) +0\nReady\nsave\nReady\ncompile\nReady\nSY:[1,2]\nHWORLD.BAS 1 \nHWORLD.BAC 7C\nTotal of 8 blocks in 2 files in SY:[1,2]\nReady\n\n## DCL (Digital Command Language)\nStarting with Version 9, **DCL** became the primary startup **RTS** even though it does not have the ability to execute binary programs.\nThis became possible with the advent of the disappearing RSX **RTS** (see below).\n**DCL** was incorporated into all of the recent versions of DEC's operating systems (RSX-11, RT-11, [VMS](https://bliptext.com/articles/openvms), and later Open[VMS](https://bliptext.com/articles/openvms)) for compatibility.\nThe standard **DCL** prompt is the dollar \"$\" sign (example):\n\n## RSX (Realtime System eXecutive)\nPrograms that were written for the RSX ****RTS**** such as COBOL, Macro Assembler, or later releases of BASIC-Plus-2, could use the maximum amount of memory available for a binary program (56K due to the requirements of an ****RTS**** needing the top 8K to use for itself).\nRSTS Version 7 and later allowed the RSX **RTS** to be included in the kernel, making it completely \"disappear\" from the user address space, thus allowing 64K bytes of memory for user programs.\nPrograms got around the limitations of the amount of available memory by using libraries (when permissible), by complicated overlay strategies, or by calling other programs (\"Chaining\") and passing them commands and data in a shared memory area called \"Core Common,\" among other practices.\nWhen RSX is the default **KBM**, the standard RSX prompt (both logged in and logged out) is the \">\" (or MCR \"Monitor Console Routine\") sign (example):\n\n## RT-11\nThe RT-11 **RTS** emulated the Single Job version of the RT-11 distribution.\nLike the RSX emulation, RT-11 occupied the top 8K of memory, leaving the bottom 56K for **CUSPS**, programs written in FORTRAN-IV or Macro Assembler.\nWhen RT-11 is the default **KBM**, the standard RT-11 prompt (both logged in and logged out) is the \".\"\nsign (example):\n\n## TECO (Text Editor and COrrector)\nThe [TECO editor](https://bliptext.com/articles/teco-text-editor) was itself implemented as an RTS to maximize the amount of memory available for the editing buffer, and also because it was first implemented in RSTS V5B, before the release of the general purpose runtime systems (RSX and RT11).\nTECO was the only RTS distributed with RSTS that did not contain a built-in KBM.\nThe user would start up TECO (like any other program) by running a TECO program (TECO.TEC).\nTECO and the affine QEDIT were the direct ancestors of the first UNIX-based text editor, ED.\nMost RSTS systems used CCL's to create a file (MAKE filespec), edit a file (TECO filespec), or run a TECO program (MUNG filespec, data).\nThe following program is an example of how TECO could be used to calculate [pi](https://bliptext.com/articles/pi) (currently set to 20 digits):\n\n# RSTS easter eggs\n\n## System start-up (INIT.SYS)\nIf a user typed an unrecognized command at system boot to the \"Option:\" prompt of INIT.SYS, the startup utility, the message \"Type 'HELP' for help\" was displayed.\nIf the user subsequently typed 'HELP' (including the quotes) to the prompt, the response was \"How amusing, anyway...\"\nfollowed by the actual help message.\n\n## PDP-11 console lights\nA system manager could compile into the kernel a rotating display pattern that gave the illusion of two snakes chasing each other around the console lights.\nThe normal kernel would give the illusion of one snake moving from right to left in the data lights across the bottom.\nIf the system manager also compiled the \"lights\" object module the user would see an additional snake moving from left to right in the address lights across the top.\nThis was accomplished by using supervisory mode in the versions prior to 9.0.\nRSX also had a similar display pattern that would appear as if two snakes were playing chicken and would run into each other in the center of the console.\n\n## Teco easter egg\nThe command 'make' allowed a user to make a text file and automatically enter the TECO text editor.\nIf a user typed 'make love', the system created a file called 'love' and typed back, 'Not War?'\n\n## Open Files List\nKevin Herbert, later working for DEC, added an undocumented feature in the 90's to allow a user to enter ^F to see a list of open files the user process had, complete with blocks in use and file sizes.\n\n## Stardate\nBeginning with version 9.0, an [undocumented feature](https://bliptext.com/articles/undocumented-feature) would allow the system manager to change the display of the system date.\nRSTS became the first operating system that would display the system date as a set of numbers representing a [stardate](https://bliptext.com/articles/stardate) as commonly known from the TV series Star Trek.\n\n# Add-ons by other companies\n[System Industries](https://bliptext.com/articles/system-industries) bought the only source license for RSTS to implement an enhancement called (SImultaneous Machine ACceSs), which allowed their special disk controller to set a semaphore flag for disk access, allowing multiple WRITES to the same files on a RSTS System where the disk is shared by multiple PDP-11 RSTS systems.\nThis feature was implemented in System Industries controllers that were attached to many DEC computers and designed by Dr. Albert Chu while he worked at System Industries.\nThe main innovation was use of a [semaphore](https://bliptext.com/articles/semaphore-programming), a flag to indicate which processor, by cooperative sharing, has exclusive write access.\nThis required many changes to the way access to disks was accomplished by the RSTS operating system.\nThe FIPS (File Information Processing System) system, that handled i/o access, was single-threaded in RSTS.\nTo allow a disk access to stall while another machine had active access to a block, required that the FIPS could timeout a request, go to the next request and 'come back' to the stalled one in a [round robin](https://bliptext.com/articles/round-robin-scheduling) fashion.\nThe code to allow this was written by Philip Hunt while working at System Industries, in [Milpitas, California](https://bliptext.com/articles/milpitas-california).\nHe eventually worked for Digital Equipment in the New England area in the late 1980s and early 1990s.\nSIMACS was not limited to the PDP-11 product line; VAXen could also use it.\n\n# RSTS emulations\n\n## ROSS/V\nIn 1981, Evans Griffiths & Hart marketed the ROSS/V product.\nROSS/V allowed all user mode processes of RSTS (**CUSPS**, **RTS**s and user programs) the ability to run unmodified under VMS on the VAX-11 machines.\nThe code for this emulation handled all of the kernel processes that would normally be handled by a RSTS kernel running on a PDP-11.\nThe original BASIC-PLUS language that has carried through all versions of RSTS was subcontracted by Evans Griffiths & Hart, Inc. for a fixed price of $10,500.\n\n## Other PDP-11 emulators\nRSTS and its applications can run under a number of PDP-11 emulators such as [SIMH](https://bliptext.com/articles/simh) and [Ersatz-11](https://bliptext.com/articles/pdp-11).\nFor more information, see [PDP-11](https://bliptext.com/articles/pdp-11).\n\n# RSTS mascot\n\n## Spike and Albert\n\n# Versions\nRSTS was originally called BTSS (Basic Time Sharing System).\nBefore shipment began, the name was changed from BTSS to RTSS because a product called BTSS was already being marketed by [Honeywell](https://bliptext.com/articles/honeywell).\nA simple typing mistake changed the name from RTSS to RSTS.\nThe addition of new memory management support and the ability to install more memory in the PDP-11/40 and PDP-11/45 led to another name change: RSTS-11 now became RSTS/E.\n\n## Clones in the USSR\n\n# Applications\nComputer [bureaus](https://bliptext.com/articles/service-bureau) sometimes deployed User-11 for RSTS/E-based [data management](https://bliptext.com/articles/data-management).","revisionCount":0},"hasMore":false,"nextCursor":null}

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