History
The GECOS-II operating system was developed by General Electric for the 36-bit GE-635 in 1962-1964. It bore a close resemblance architecturally to the IBM DOS/360. However, the GE-635 architecture was very different from the IBM System/360 and GECOS was more ambitious than DOS/360. GECOS-II supported both time-sharing (TSS) and batch processing, with dynamic allocation of memory (IBM had fixed partitions, at that time), making it a true second-generation operating system.
After Honeywell acquired GE's computer division, GECOS-III was renamed GCOS 3, and the hardware line was renamed to the H-6000 adding the EIS (enhanced instruction set, character oriented instead of word oriented). Later Honeywell Marketing created a "Series" 60, and renamed the H-6000 to the Level 66 (later on, DPS 8). Honeywell, along with its European affiliate CII-Honeywell Bull, launched a new 32-bit product line called Level 64 (which later became the DPS 7).
The name "GCOS" was extended to the operating systems for all Honeywell-marketed product lines. GCOS-64, a completely different 32-bit operating system for the Level 64 series, significantly inspired by a parallel development called "Multics", was designed by Honeywell and Honeywell Bull developers in France and Boston. GCOS-62, the operating system for another 32-bit low-end line of machines, the Level 62 series, was designed in Italy. GCOS-61 was the operating system for a new version of a small system made in France (Model 58, later Level 61/58), and the operating system for a new 16-bit minicomputer line from Massachusetts (Billerica), the Level 6, got the name GCOS 6.
Another renaming of the hardware product lines occurred in 1979, with the Level 6 becoming the DPS 6, the Level 62 becoming the DPS 4, the Level 64 becoming DPS 7, and Level 66 becoming DPS 8. Operating Systems retained the GCOS brand-name, with GCOS 6, GCOS 4, GCOS 7, and GCOS 8 being introduced. GCOS 8 was an extensive rewrite of GCOS 3, with changes made to support true virtual memory management and demand paging (these changes also required new hardware). GCOS 3 was supported in maintenance for several years after this announcement and renaming.
GCOS 3 (and later GCOS 7 and GCOS 8) featured a good Codasyl "relational" database called Integrated Data Store (IDS) that was the model for the more successful IDMS.
Several transaction processing monitors were designed for GCOS 3 and GCOS 8. An early attempt at TP for GCOS 3, the Transaction Processing Executive, assumed that, as in Unix, a new process should be started to handle each transaction, and enjoyed only very limited success. Another TP system, the Transaction Driven System (TDS), was soon developed for GCOS 3, using a single process (potentially with multiple threads) to service all transactions. TDS was essentially a Honeywell development. It was later replaced by the backward-compatible Transaction Processing 8 (TP8) on GCOS 8, which profited from the overhaul in GCOS system architecture that came with GCOS 8 to make full use of virtual memory concepts. TP8 used multiple static processes in a way similar to UNIX daemons to handle incoming transactions in a multiplexed way. TDS and its TP8 successor were commercially successful, and TDS predated IBM CICS, which had a very similar architecture. A similar product also called TDS was developed for GCOS-7, but the internal architecture was completely different.
DPS 6 and DPS 4 (ex-Level 62) were superseded by Motorola 68000- and later on PowerPC minicomputers running Unix and the product lines were discontinued, though GCOS 6 ran in an emulator on top of AIX. The DPS 7 line, along with GCOS 7, continued to evolve into the DPS 7000 hardware base.
In the late 1980s Honeywell sold its computer business to a joint venture that initially included NEC and Bull, with Honeywell still holding a stake for a time. Over a couple of years, Bull took over the company. NEC supplied several generations of mainframe hardware at the high end, which would run both GCOS 8 and their own ACOS-4 Operating System. Bull used the nomenclature DPS-9000 for its entire GCOS 8-based mainframe line, which included models designed by both Bull and NEC.
By the late 1990s and early 2000s, Bull's desire was to center its development on a single hardware base, running commodity Intel chips but with Bull value-adds. This platform, called Novascale and based on Itanium 2 processors, runs both Windows and Linux natively. However, Instruction Set Simulators for both the DPS 7000 and DPS 9000 allowed GCOS 7 and GCOS 8 to run on this platform. GCOS 7 has also been ported to a lower-end Xeon-based platform, while Bull has publicly stated that GCOS 8 will continue to be developed for Itanium systems. Bull continues to invest development money in support of both GCOS 7 and GCOS 8, and still has customers in countries around the world.
A trace of GCOS influence remains today in modern UNIX systems. Some early Unix systems at Bell Labs used GCOS machines for print spooling and various other services. The field added to "/etc/passwd" to carry GCOS ID information was called the "GECOS field" and survives today as the "pw_gecos" member used for the user's full name and other human-ID information.
Read more about this topic: General Comprehensive Operating System
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