The TOPS-20 operating system by Digital Equipment Corporation (DEC) is a proprietary[1] OS used on some of DEC's 36-bit mainframe computers. The Hardware Reference Manual was described as for "DECsystem-10/DECSYSTEM-20 Processor" (meaning the DEC PDP-10 and the DECSYSTEM-20).[2]
 login | |
| Developer | Digital Equipment Corporation |
|---|---|
| Written in | Assembly language |
| OS family | TENEX |
| Working state | Discontinued |
| Initial release | 1976 |
| Latest release | 7.1 / June 1988 |
| Marketing target | Mainframe computers |
| Available in | English |
| Platforms | PDP-10 |
| Default user interface | Command-line interface |
| License | Proprietary |
| Preceded by | TENEX |
TOPS-20 began in 1969 as the TENEX operating system of Bolt, Beranek and Newman (BBN) and shipped as a product by DEC starting in 1976.[3] TOPS-20 is almost entirely unrelated to the similarly named TOPS-10, but it was shipped with the PA1050 TOPS-10 Monitor Calls emulation facility which allowed most, but not all, TOPS-10 executables to run unchanged. As a matter of policy, DEC did not update PA1050 to support later TOPS-10 additions except where required by DEC software.
TOPS-20 competed with TOPS-10, ITS[4] and WAITS—all of which were notable time-sharing systems for the PDP-10 during this timeframe. TOPS-20 is informally known as TWENEX.[5]
TENEX
editTOPS-20 was based upon the TENEX operating system, which had been created by Bolt Beranek and Newman for Digital's PDP-10 computer. After Digital started development of the KI-10 version of the PDP-10, an issue arose: by this point TENEX was the most popular customer-written PDP-10 operating systems, but it would not run on the new, faster KI-10s. To correct this problem, the DEC PDP-10 sales manager purchased the rights to TENEX from BBN and set up a project to port it to the new machine. In the end, very little of the original TENEX code remained, and Digital ultimately named the resulting operating system TOPS-20.
PA1050
editSome of what came with TOPS-20 was merely an emulation of the TOPS-10 Operating System's calls. These were known as UUO's, standing for Unimplemented User Operation,[6] and were needed both for compilers, which were not 20-specific, to run, as well as user-programs written in these languages. The package that was mapped into a user's address space was named PA1050: PA as in PAT as in compatibility; 10 as in DEC or PDP 10; 50 as in a PDP 10 Model 50, 10/50, 1050.[7]
Sometimes PA1050 was referred to as PAT, a name that was a good fit to the fact that PA1050, "was simply unprivileged user-mode code" that "performed the requested action, using JSYS calls where necessary."[7]
TOPS-20 capabilities
editThe major ways to get at TOPS-20 capabilities, and what made TOPS-20 important, were
- Commands entered via the command processor, EXEC.EXE[2]
- JSYS (Jump to System) calls from MACro-language (.MAC) programs[8][9]
The "EXEC" accomplished its work primarily using
- internal code, including calls via JSYS
- requesting services from "GALAXY" components (e.g. spoolers)
Command processor
editRather advanced for its day were some TOPS-20-specific features:
- Command completion[3]
- Dynamic help in the form of
- noise-words - typing DIR and then pressing the ESCape key resulted in
- DIRectory (of files)
- typing I and pressing the Esc key resulted in
- Information (about)
One could then type ? to find out what operands were permitted/required. Pressing Ctrl-T displays status information.
Commands
editThe following list of commands are supported by the TOPS-20 Command Processor.[2]
- ACCESS
- ADVISE
- APPEND
- ARCHIVE
- ASSIGN
- ATTACH
- BACKSPACE
- BLANK
- BREAK
- BUILD
- CANCEL
- CLOSE
- COMPILE
- CONNECT
- CONTINUE
- COPY
- CREATE
- CREF
- CSAVE
- DAYTIME
- DDT
- DEASSIGN
- DEBUG
- DEFINE
- DELETE
- DEPOSIT
- DETACH
- DIRECTORY
- DISABLE
- DISCARD
- DISMOUNT
- EDIT
- ENABLE
- END-ACCESS
- EOF
- ERUN
- EXAMINE
- EXECUTE
- EXPUNGE
- FDIRECTORY
- FORK
- FREEZE
- GET
- HELP
- INFORMATION
- KEEP
- LOAD
- LOGIN
- LOGOUT
- MERGE
- MODIFY
- MOUNT
- PERUSE
- PLOT
- POP
- PUNCH
- PUSH
- RECEIVE
- REENTER
- REFUSE
- REMARK
- RENAME
- RESET
- RETRIEVE
- REWIND
- RUN
- SAVE
- SEND
- SET
- SET HOST
- SKIP
- START
- SUBMIT
- SYSTAT
- TAKE
- TALK
- TDIRECTORY
- TERMINAL
- TRANSLATE
- TYPE
- UNATTACH
- UNDELETE
- UNKEEP
- UNLOAD
- VDIRECTORY
JSYS features
editJSYS stands for Jump to SYStem.[10] Operands were at times memory addresses. "TOPS-20 allows you to use 18-bit or 30-bit addresses. Some monitor calls require one kind, some the other; some calls accept either kind. Some monitor calls use only 18 bits to hold an address. These calls interpret 18-bit addresses as locations in the current section."[2]
Internally, files were first identified, using a GTJFN (Get Job File Number) JSYS, and then that JFN number was used to open (OPENF) and manipulate the file's contents.
PCL (Programmable Command Language)
editPCL (Programmable Command Language) is a programming language that runs under TOPS-20. PCL source programs are, by default, stored with Filetype .PCL, and enable extending the TOPS-20 EXEC via a verb named DECLARE. Newly compiled commands then become functionally part of the EXEC.[11][12][13][14]
PCL language features
editPCL includes:[11]
- flow control: DO While/Until, CASE/SELECT, IF-THEN-ELSE, GOTO
- character string operations (length, substring, concatenation)
- access to system information (date/time, file attributes, device characteristics)
TOPS-20 today
editPaul Allen maintained several publicly accessible historic computer systems before his death, including an XKL TOAD-2 running TOPS-20.
See also SDF Public Access Unix System.
See also
editReferences
edit- ^ Richard Stallman (30 October 1986). "RMS lecture at KTH (Sweden)".
- ^ a b c d "TOPS-20 Command manual" (PDF). Digital Equipement Corporation. September 1985.
- ^ a b "Origins and Development of TOPS-20".
- ^ "ITS reference manual" (PDF).
- ^ "TWENEX". The Jargon File.
- ^ "What does UUO mean in Software?". abbreviations.com.
- ^ a b The 10/50 was the top-of-the-line KA machine at that time. Dan Murphy (1989). "Origins and Development of TOPS-20". The family continued with another KA, the 10/55, and then came KI, KL & KS.
- ^ The JSYS was the counterpart for the 20 of what was done by TOPS-10 on a "10" and thus the emulator for a DEC PDP-10 Model 50 was what PA1050 was emulating. The 10's system calls were known as UUO's
- ^ "DECSYSTEM-20 Assembly Language Guide". The Kermit Project. 3 July 1980.
- ^ "JSYS means Jump to System". allacronyms.com.
- ^ a b TOPS-20 Programmable Command Language / User's Guide and Reference Manual. Carnegie Mellon University Computation Center. 1981.
- ^ "Programmable Command Language". fileformats.archiveteam.org. March 11, 2016.
- ^ R. J. Cohn (1988). "Programmable Command Languages for Window System" (PDF). Archived from the original (PDF) on 2003-09-26.
- ^ Ray Scott (12 January 1983). "TOPS-20 Programmable Command Language". Archived from the original on 2008-10-07.
Further reading
edit- Storage Organization and Management in TENEX. Daniel L. Murphy. AFIPS Proceedings, 1972 FJCC.
- Implementation of TENEX on the KI10. Daniel L. Murphy. TENEX Panel Session, NCC 1974.
- "TOPS-20 User's Guide Archived 2014-01-07 at the Wayback Machine." 1988.
- "DECSYSTEM-20 Assembly Language Guide." Frank da Cruz and Chris Ryland, 1980.
- "Running TOPS-20 V4.1 under the SIMH Emulator."
External links
edit- DIGITAL Computing Timeline
- Origins and Development of TOPS-20 is an excellent longer history.
- Panda TOPS-20 distribution.
- SDF Public Access TWENEX.
- SIMH Simulator capable of simulating the PDP-10 and running TOPS-20.
- Manuals for DEC 36-bit computers Archived 2014-03-02 at the Wayback Machine.
- PDP-10 Software Archive.
- 36-bits Forever.
- Request a login to Living Computers: Museum + Labs TOAD-2 running TOPS-20.