General Comprehensive Operating System
Encyclopedia
General Comprehensive Operating System (GCOS, icon) is a family of operating system
s oriented toward mainframe computer
s.
The original version of GCOS was developed by General Electric
from 1962; originally called GECOS (the General Electric Comprehensive Operating Supervisor). The operating system is still used today in its most recent version (GCOS 8) on servers and mainframes produced by Honeywell and Groupe Bull
, primarily through emulation, to provide continuity with legacy mainframe environments.
Although GCOS has a basic architecture similar to that of the IBM 360 and subsequent operating systems with which it competed, it was also heavily influenced by projects such as MEDINET, Multics
, and WWMCCS, and has inherited a strong security structure in consequence. Hardware and software features combine to render the operating system unusually secure for an operating system of its generation and class. Multics influenced the design of the hardware, with gate-oriented secure transfer-of-control instructions and a hardware-enforced system of security levels very similar to that of the famous Multics rings. Operational environments such as WWMCCS drove development of special security features to allow secure hosting of classified information and compartmentalization. For a time separate versions of the GCOS system with special security features turned on were maintained specifically for government customers.
GCOS is a process-oriented OS, in which each process hosts one or more execution threads and executes in its own virtual memory space. Virtual memory is divided into segments of arbitrary size reminiscent of Multics segments, and a second level of address translation converts pure virtual addresses to pageable addresses, which are then converted to real addresses in main memory or backing store. Segments and pages and other constructs include hardware-enforced security parameters. The top-level virtual memory architecture also simplifies sharing of code and data in a secure fashion, again in a way reminiscent of Multics.
GCOS requires specific hardware designed for the operating system, although the most recent machines capable of running the OS do so through emulation. The hardware originally had much in common with Multics hardware, so much so that some mainframe equipment could be switched from "GCOS mode" to "Multics mode" with the turn of a dial. Much of the peripheral equipment used with GCOS shared a great deal with Multics, although front-end network processors were very different between the two systems.
. Datanet was the communications front end for GCOS while its successor MainWay supports both DSA and TCP/IP networks. The Questar series provided VIP terminals for the DSA environment. TNVIP (VIP over IP) is used for the terminal emulation in a TCP/IP environment (GLink, Winsurf).
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 Europe
an 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 sytem 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 Simulator
s 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.
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s oriented toward mainframe computer
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
s.
The original version of GCOS was developed by General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
from 1962; originally called GECOS (the General Electric Comprehensive Operating Supervisor). The operating system is still used today in its most recent version (GCOS 8) on servers and mainframes produced by Honeywell and Groupe Bull
Groupe Bull
-External links:* * — Friends, co-workers and former employees of Bull and Honeywell* *...
, primarily through emulation, to provide continuity with legacy mainframe environments.
System architecture and concepts
GCOS is a multithreading, multiprogramming operating system originally oriented towards batch processing, although later versions incorporated enhancements for timesharing and online transaction processing environments. Systems running GCOS today use it mainly for batch and OLTP, or as a backend enterprise server.Although GCOS has a basic architecture similar to that of the IBM 360 and subsequent operating systems with which it competed, it was also heavily influenced by projects such as MEDINET, Multics
Multics
Multics was an influential early time-sharing operating system. The project was started in 1964 in Cambridge, Massachusetts...
, and WWMCCS, and has inherited a strong security structure in consequence. Hardware and software features combine to render the operating system unusually secure for an operating system of its generation and class. Multics influenced the design of the hardware, with gate-oriented secure transfer-of-control instructions and a hardware-enforced system of security levels very similar to that of the famous Multics rings. Operational environments such as WWMCCS drove development of special security features to allow secure hosting of classified information and compartmentalization. For a time separate versions of the GCOS system with special security features turned on were maintained specifically for government customers.
GCOS is a process-oriented OS, in which each process hosts one or more execution threads and executes in its own virtual memory space. Virtual memory is divided into segments of arbitrary size reminiscent of Multics segments, and a second level of address translation converts pure virtual addresses to pageable addresses, which are then converted to real addresses in main memory or backing store. Segments and pages and other constructs include hardware-enforced security parameters. The top-level virtual memory architecture also simplifies sharing of code and data in a secure fashion, again in a way reminiscent of Multics.
GCOS requires specific hardware designed for the operating system, although the most recent machines capable of running the OS do so through emulation. The hardware originally had much in common with Multics hardware, so much so that some mainframe equipment could be switched from "GCOS mode" to "Multics mode" with the turn of a dial. Much of the peripheral equipment used with GCOS shared a great deal with Multics, although front-end network processors were very different between the two systems.
Distributed Systems Architecture
The networking architecture, developed by Honeywell-Bull for the GCOS environment, was Distributed Systems Architecture (DSA). Distributed Systems Architecture was strictly compliant with Open Systems InterconnectionOpen Systems Interconnection
Open Systems Interconnection is an effort to standardize networking that was started in 1977 by the International Organization for Standardization , along with the ITU-T.-History:...
. Datanet was the communications front end for GCOS while its successor MainWay supports both DSA and TCP/IP networks. The Questar series provided VIP terminals for the DSA environment. TNVIP (VIP over IP) is used for the terminal emulation in a TCP/IP environment (GLink, Winsurf).
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 IBMIBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
DOS/360
DOS/360
Disk Operating System/360, also DOS/360, or simply DOS, was an operating system for IBM mainframes. It was announced by IBM on the last day of 1964, and it was first delivered in June 1966....
. 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
Time-sharing
Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.By allowing a large...
(TSS) and batch processing
Batch processing
Batch processing is execution of a series of programs on a computer without manual intervention.Batch jobs are set up so they can be run to completion without manual intervention, so all input data is preselected through scripts or command-line parameters...
, with dynamic allocation of memory (IBM had fixed partitions, at that time), making it a true second-generation operating system.
After Honeywell
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
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 Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an affiliate CII-Honeywell Bull
Groupe Bull
-External links:* * — Friends, co-workers and former employees of Bull and Honeywell* *...
, 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
Multics
Multics was an influential early time-sharing operating system. The project was started in 1964 in Cambridge, Massachusetts...
", was designed by Honeywell and Honeywell Bull developers in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...
. GCOS-62, the operating system for another 32-bit low-end line of machines, the Level 62 series, was designed in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. GCOS-61 was the operating sytem 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
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
line from Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
(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
CODASYL
CODASYL is an acronym for "Conference on Data Systems Languages". This was a consortium formed in 1959 to guide the development of a standard programming language that could be used on many computers...
"relational" database
Database management system
A database management system is a software package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators and other specialists. A database is an integrated...
called Integrated Data Store
Integrated Data Store
Integrated Data Store is a network database largely used by industry for its performance.IDS was designed by Charles Bachman at General Electric in the 1960s. It was not known to be easy to use or implement applications with, because it was designed to maximize performance using the hardware...
(IDS) that was the model for the more successful IDMS
IDMS
IDMS is primarily a network database management system for mainframes. It was first developed at B.F. Goodrich and later marketed by Cullinane Database Systems...
.
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
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
, a new process
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
should be started to handle each transaction
Database transaction
A transaction comprises a unit of work performed within a database management system against a database, and treated in a coherent and reliable way independent of other transactions...
, 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
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
- and later on PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
minicomputers running Unix and the product lines were discontinued, though GCOS 6 ran in an emulator
Emulator
In computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...
on top of AIX
AIX operating system
AIX AIX AIX (Advanced Interactive eXecutive, pronounced "a i ex" is a series of proprietary Unix operating systems developed and sold by IBM for several of its computer platforms...
. 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
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
natively. However, Instruction Set Simulator
Instruction Set Simulator
An instruction set simulator is a simulation model, usually coded in a high-level programming language, which mimics the behavior of a mainframe or microprocessor by "reading" instructions and maintaining internal variables which represent the processor's registers.Instruction simulation is a...
s 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
Xeon
The Xeon is a brand of multiprocessing- or multi-socket-capable x86 microprocessors from Intel Corporation targeted at the non-consumer server, workstation and embedded system markets.-Overview:...
-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
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
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
Gecos field
The gecos field, or GECOS field is an entry in the /etc/passwd file on Unix, and similar operating systems.It is typically used to record general information about the account or its user such as their real name and phone number.-Format:...
" and survives today as the "pw_gecos" member used for the user's full name and other human-ID information.
See also
- Timeline of operating systems
- Mainframe computerMainframe computerMainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
- Advanced Comprehensive Operating SystemAdvanced Comprehensive Operating SystemAdvanced Comprehensive Operating System is a family of mainframe computer operating systems developed by NEC for the Japanese market. It consists of three systems, based on the General Comprehensive Operating System family developed by General Electric, Honeywell, and Bull...
External links
- GCOS 8 Mainframes - The Groupe Bull GCOS8 product.