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265:. BBN started talks with DEC to get a paging subsystem in the new machine, then known by its CPU name, the KA-10. DEC was not interested; however, one development of these talks was support in the PDP-10 for a second virtual memory segment, allowing half of the user address space to be mapped to a separate (potentially read-only) region of physical memory. Additionally, DEC insisted on keeping the cost of the machine as low as possible, such as supporting systems with a minimum of 16K words of core, and omitting the fast semiconductor
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running with minimum effort. This would require a re-write of TOPS-10 to support the paging system, and this seemed like a major problem. At the same time, TOPS-10 did not support a number of features the developers wanted. In the end they decided to make a new system, but include an emulation library that would allow it to run existing TOPS-10 software with minor effort.
249:. DEC was still heavily involved with MIT's AI Lab, and many feature requests from the LISP hackers were moved into this machine. 36-bit computing was especially useful for LISP programming because with an 18-bit address space, a word of storage on these systems contained two addresses, a perfect match for the common LISP
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operating system killed the DEC-20 and put an end to TWENEX's brief period of popularity. DEC attempted to convince TOPS-20 users to convert to VMS, but instead, by the late 1980s, most of the TOPS-20 users had migrated to Unix. A loyal group of TOPS-20 enthusiasts kept working on various projects to
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line of computers. DEC visited them and many of their ideas were then folded into the KL-10 project. The same year IBM also announced their own machine with virtual memory, making it a standard requirement for any computer. In the end the KL integrated a number of major changes to the system, but did
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BBN nevertheless went ahead with its purchase of several PDP-10s, and decided to build their own hardware pager. During this period a debate began on what operating system to run on the new machines. Strong arguments were made for the continued use of TOPS-10, in order to keep their existing software
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program could do so at the same time. The pager system would handle mapping as it would always, copying data to and from the backing store as needed. The only change needed was for the pager to be able to hold several sets of mappings between RAM and store, one for each program using the system. The
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The first in-house code name for the operating system was VIROS (VIRtual memory
Operating System); when customers started asking questions, the name was changed to SNARK so that DEC could truthfully deny that there was any project called VIROS. When the name SNARK became known, the name was briefly
412:
hardware revision to enlarge the user virtual address space. Some effective address calculations by instructions located beyond the original 18-bit address space were performed to 30 significant bits, although only a 23-bit virtual address space was supported. Program code located in the original
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operations. BBN became interested in buying one for their AI work when they became available, but wanted DEC to add a hardware version of Murphy's pager directly into the system. With such an addition, every program on the system would have paging support invisibly, making programming much easier.
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TENEX became fairly popular in the small PDP-10 market, and the external pager hardware developed into a small business of its own. In early 1970 DEC started work on an upgrade to the PDP-10 processor, the KI-10. BBN once again attempted to get DEC to support a complex pager with indirect page
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it to the new machine. At around this time Murphy moved from BBN to DEC as well, helping on the porting project. Most of the work centered on emulating the BBN pager hardware in a combination of software and the KI-10's simpler hardware. The speed of the KI-10 compared to the PDP-6 made this
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tables, but instead DEC decided on a much simpler single-level page mapping system. This compromise impacted system sales; 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.
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DEC was initially interested, however in 1966 they announced they would be discontinuing the PDP-6 and concentrating solely on their smaller 18-bit and new 16-bit lines. The PDP-6 was expensive and complex, and therefore had not sold well.
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with the full command. The completion feature also worked with file names, which took some effort on the part of the interpreter, and the system allowed for long file names with human-readable descriptions. TENEX also included a
356:), printed out a list of possible matching commands and then return the user to the command line with the question mark removed. The command line completion and help live on in current CLIs like
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system that understood unambiguously abbreviated command words, and expanded partial command words into complete words or phrases. For instance, the user could type
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pager also held access time information in order to tune performance. The resulting pager was fairly complex, filling a full-height 19" rackmount chassis.
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TWENEX was successful and very popular; in fact, there was a period in the early 1980s when it commanded as fervent a culture of partisans as
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Just as the new TENEX was shipping, DEC started work on the KL-10, intended to be a low-cost version of the KI-10. While this was going on,
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language, allowing it to write out unused portions of memory to disk for later recall if needed. One such system had been developed for the
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and included nowhere near the required amount. The pager used the most significant bits of the address to index a table of blocks on a
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of "twenty TENEX"), even though by this point very little of the original TENEX code remained (analogously to the differences between
392:, were working on their own project to build a PDP-10 that was ten times faster than the original KA-10. The project evolved into the
333:" was noise added to make the purpose of the command clearer. To relieve users of the need to type these long commands, TENEX used a
448:). DEC people cringed when they heard "TWENEX", but the term caught on nevertheless (the written abbreviation "20x" was also used).
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To correct this problem, the DEC PDP-10 sales manager purchased the rights to TENEX from BBN and set up a project to
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Ultimately DEC picked TOPS-20 as the name of the operating system, and it was as TOPS-20 that it was marketed. The
313:. Unlike typical systems of the era, TENEX deliberately used long command names and even included non-significant
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Functional upgrades for the KL-10 processor architecture were limited. The most significant new feature (called
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system—that is, not only could programs access a full 18 bit address space of 262144 words of virtual memory,
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reversed to become KRANS; this was quickly abandoned when someone objected that "
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option (substituting core), at the cost of a considerable performance decrease.
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429:(though it simply means "wreath"; this part of the story may be apocryphal).
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It was not long until it became clear that DEC was once again entering the
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to further expand the commands for clarity. For instance, Unix uses
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Some text in this article was taken from The Jargon File entry on "
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possible. Additionally the porting effort required a number of new
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would run a version of TENEX as its default operating system.
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not end up being any lower in cost. From the start, the new
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to print a list of files in a directory, whereas TENEX used
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to support the newer backing store devices being used.
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and the escape key, at which point TENEX would replace
436:, mindful of its origins, quickly dubbed it TWENEX (a
309:One notable feature of TENEX was its user-oriented
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413:18-bit address space had unchanged semantics, for
570:TENEX, A Paged Time Sharing System for the PDP-10
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520:"Technical Details of the BBN Pager Model 701"
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226:memory. The machines were based on expensive
222:word, allowing addresses to encode for a 256
408:) was modified pager microcode running on a
514:Strollo, Theodore R.; Burchflel, Jerry D.;
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658:Compatible Time-Sharing System (CTSS)
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576:, Vol. 15, pages 135–143, March 1972.
468:preserve and extend TOPS-20, notably
352:help system: typing a question mark (
472:and the Panda TOPS-20 distribution.
261:business with what would become the
160:, which later formed the basis for
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289:The developer team—amongst them
673:Cray Time Sharing System (CTSS)
868:Time-sharing operating systems
863:Discontinued operating systems
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1:
625:Time-sharing system evolution
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482:Time-sharing system evolution
388:AI programmers, many of them
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162:Digital Equipment Corporation
425:" meant "funeral wreath" in
214:before he joined BBN. Early
180:was involved in a number of
16:1969 Operating system by BBN
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643:Berkeley Timesharing System
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65:; 55 years ago
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245:In 1964 DEC announced the
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527:Bolt, Beranek and Newman
311:command line interpreter
638:BBN Time-Sharing System
186:artificial intelligence
560:, Jerry D. Burchfiel,
415:backward compatibility
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116:Command-line interface
566:Raymond S. Tomlinson
516:Tomlinson, Raymond S.
463:architecture and its
364:From TENEX to TOPS-20
281:BBN Pager, circa 1970
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152:developed in 1969 by
323:DIRECTORY (OF FILES)
497:", which is in the
406:extended addressing
386:Stanford University
350:command recognition
82:Mainframe computers
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336:command completion
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518:(July 22, 1970).
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738:ORVYL and WYLBUR
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558:Daniel G. Bobrow
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134:Succeeded by
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315:noise words
251:CAR and CDR
228:core memory
128:Proprietary
857:Categories
653:CDC Kronos
488:References
390:MIT alumni
331:(OF FILES)
172:Background
41:Written in
327:DIRECTORY
88:Platforms
29:Developer
842:Category
713:MUSIC/SP
541:"TWENEX"
476:See also
442:AT&T
267:register
224:kiloword
156:for the
55:Historic
783:TOPS-20
778:TOPS-10
733:OpenVMS
708:Multics
427:Swedish
410:Model B
184:-based
166:TOPS-20
138:TOPS-20
123:License
109:Default
102:TOPS-10
68: (
840:
818:VPS/VM
813:VP/CSS
758:RSTS/E
743:OS4000
728:NOS/VE
668:CP/CMS
495:TWENEX
394:Foonly
263:PDP-10
259:36-bit
220:18-bit
195:paging
158:PDP-10
148:is an
92:PDP-10
823:WAITS
793:TSS/8
763:TENEX
718:NLTSS
698:MCTSS
523:(PDF)
423:krans
303:every
247:PDP-6
204:PDP-1
190:DARPA
146:TENEX
23:TENEX
798:Unix
773:TSOS
748:Pick
693:LTSS
683:EMAS
678:DTSS
453:Unix
374:port
358:tcsh
293:and
200:LISP
182:LISP
70:1969
63:1969
803:UTS
788:TSS
768:TSO
753:RAX
723:NOS
703:MTS
688:ITS
663:COS
572:",
568:, "
465:VMS
461:VAX
457:ITS
455:or
446:BSD
345:DIR
341:DIR
325:. "
240:RAM
216:DEC
210:by
208:MIT
206:at
178:BBN
164:'s
154:BBN
34:BBN
859::
808:VM
564:,
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319:ls
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603:e
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354:?
72:)
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