TOPS-20

TOPS-20
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DeveloperDigital Equipment Corporation
Written inAssembly language
OS familyTENEX
Working stateDiscontinued
Initial release1976; 48 years ago (1976)
Latest release7.1 / June 1988; 36 years ago (1988-06)
Marketing targetMainframe computers
Available inEnglish
PlatformsPDP-10
Default
user interface
Command-line interface
LicenseProprietary
Preceded byTENEX

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]

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]

  1. ^ Richard Stallman (30 October 1986). "RMS lecture at KTH (Sweden)".
  2. ^ "TOPS-20 Command manual" (PDF). Digital Equipement Corporation. September 1985.
  3. ^ "Origins and Development of TOPS-20".
  4. ^ "ITS reference manual" (PDF).
  5. ^ "TWENEX". The Jargon File.