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Multics
Website Multicians[1], Sources[2]
Company/
developer		 MIT, GE, Bell Labs
Programmed in PL/I, Assembly language
Source model Semi-free[3]; Free and open source software as of 2007
Initial release 1969
Available language(s) English
Supported platforms GE-645 mainframes, Honeywell 6180 series machines
Kernel type Monolithic kernel
Default user interface Command line interface
License MIT License
Working state Mature, Historic

Multics (Multiplexed Information and Computing Service) was an extremely influential early time-sharing operating system. A website (alternatively web site or Web site, a back-construction from the Proper noun World Wide Web) is a collection of Web pages The software industry comprises businesses involved in the development, maintenance and publication of Computer software. A software developer is a person or organization concerned with facets of the software development process wider than design and coding a somewhat broader scope of Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization PL/I ("Programming Language One" ˌpiːˌɛlˈwʌn is an imperative computer Programming language designed for scientific engineering See the terminology section below for information regarding inconsistent use of the terms assembly and assembler Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Open source software (OSS began as a marketing campaign for Free software. Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. In the Philosophy of language, a natural language (or ordinary language) is a Language that is spoken or written in phonemic-alphabetic or phonemically-related English is a West Germanic language originating in England and is the First language for most people in the United Kingdom, the United States The GE-600 series was a family of 36-bit mainframe Computers originating in the 1960s built by General Electric (GE In 1970 General Electric sold their computing division to Honeywell. In Computer science, the kernel is the central component of most computer Operating systems (OS A monolithic kernel is a kernel architecture where the entire kernel is run in Kernel space in Supervisor mode. The user interface (or Human Computer Interface) is the aggregate of means by which people&mdash the users '&mdash interact with the System A software license (or software licence in commonwealth usage is a Legal instrument governing the usage or redistribution of copyright protected software The MIT License is a Free software license originating at the Massachusetts Institute of Technology (MIT used by the MIT X Consortium. Time-sharing refers to sharing a computing resource among many users by multitasking. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination The project was started in 1964. Year 1964 ( MCMLXIV) was a Leap year starting on Wednesday (link will display full calendar of the 1964 Gregorian calendar. The last known running Multics installation was shut down on October 31, 2000. Events 445 BC – Ezra reads the Book of the Law to the Israelites in Jerusalem (see Nehemiah 91 NLTse 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar.

Contents

Overview

Initial planning and development for Multics started in 1964. Year 1964 ( MCMLXIV) was a Leap year starting on Wednesday (link will display full calendar of the 1964 Gregorian calendar. Originally it was a cooperative project led by MIT (with Fernando Corbató), along with General Electric and Bell Labs. Fernando José "Corby" Corbató (born July 1, 1926 in Oakland, California) is a prominent American Computer scientist Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization Bell Labs dropped out in 1969, and in 1970 GE's computer business, including Multics, was taken over by Honeywell. Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. Year 1970 ( MCMLXX) was a Common year starting on Thursday (link shows full calendar of the Gregorian calendar. Honeywell ( is a major American multinational conglomerate company that produces a variety of consumer products engineering services and aerospace systems

Multics was conceived as a commercial product for GE and became one for Honeywell, but not a very successful one. Due to its many novel and valuable ideas, Multics had a great impact in the computer field, even though it was then much derided by its critics. [4]

It had numerous features intended to result in high availability, so that it would produce a computing utility, similar to the telephone and electricity services. Utility computing is the packaging of computing resources, such as computation and storage as a metered service similar to a traditional Public utility (such Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information To achieve this, in addition to being modular in software structure, the hardware was too, and the system could grow in size by simply adding more of the appropriate resource - computing power, main memory, disk storage, etc. Separate Access Control Lists on every file provided flexible information sharing and complete privacy when needed. In Computer security, an access control list ( ACL) is a list of permissions attached to an object It had a number of standard mechanisms to allow engineers to analyze the performance of the system, as well as a number of adaptive performance optimization mechanisms.

Novel ideas

Multics implemented a single level store for data access, discarding the clear distinction between files (called segments in Multics) and process memory. Single-level store ( SLS) is a term most often associated with the IBM System i Operating system, I5/OS, although it was originally A computer file is a block of Arbitrary Information, or resource for storing information which is available to a Computer program and is usually In computing a process is an instance of a Computer program that is being sequentially executed by a computer system that has the ability to run several computer The memory of a process consisted solely of segments which were mapped into its address space. In Computing, an address space defines a range of discrete addresses each of which may correspond to a physical or virtual Memory register, a network host To read or write to them, the process simply used normal CPU instructions, and the operating system took care of making sure that all the modifications were saved to disk. Disk storage is a general category of a Computer storage mechanisms in which data is recorded on planar round and rotating surfaces ( disks, discs, or In POSIX terminology, it was as if every file was mmap()ed; however, in Multics there was no concept of process memory, separate from the memory used to hold mapped-in files, as Unix has. POSIX (ˈpɒzɪks or "Portable Operating System Interface" is the collective name of a family of related standards specified by the IEEE to define In Computing, mmap is a POSIX -compliant Unix System call that maps files or devices into memory Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer All memory in the system was part of some segment, which appeared in the file system; this included the temporary scratch memory of the process, its kernel stack, etc. In Computing, a file system (often also written as filesystem) is a method for storing and organizing Computer files and the data they contain to make

One disadvantage of this was that the size of segments was limited to 256K 36-bit words (slightly more than 1 megabyte). A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on This was due to the particular hardware architecture of the machines Multics ran on. Extra code had to be used to work on files larger than this, called multi-segment files. But in the days when one megabyte of memory was prohibitively expensive, and before large databases and later huge bitmap graphics, this limit was rarely encountered. In Computer graphics, a bitmap or pixmap is a type of memory organization or Image file format used to store Digital images The

Another major new idea of Multics was dynamic linking, in which a running process could request that other segments be added to its address space, segments which could contain code that it could then execute. In Computer science, a library is a collection of Subroutines used to develop Software. This allowed applications to automatically use the latest version of any external routine they called, since those routines were kept in other segments, which were dynamically linked in only when a process first tried to begin execution in them. Since different processes could use different search rules, different users could end up using different versions of external routines automatically. Equally importantly, with the appropriate settings on the Multics security facilities, the code in the other segment could then gain access to data structures maintained in a different process.

Thus, to interact with an application running in part as a daemon (in another process), a user's process simply performed a normal procedure call instruction, to a code segment which it had dynamically linked to (a code segment which implemented some operation associated with the daemon). In Unix and other computer multitasking Operating systems a daemon (ˈdiːmən or /ˈdeɪmən/ is a Computer program that runs in the background The code in that segment could then modify data maintained and used in the daemon. When the action necessary to commence the request was completed, a simple procedure return instruction returned control of the user's process to the user's code.

The single-level store and dynamic linking are still not available to their full power in other widely used operating systems, despite the rapid and enormous advance in the computer field since the 1960s. The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 They are becoming more widely accepted and available in more limited forms, e. g. dynamic linking.

Multics also supported extremely aggressive on-line reconfiguration; central processing units, memory banks, disk drives, etc. could be added and removed while the system continued operating. At the MIT system, where most early software development was done, it was common practice to split the multiprocessor system into two separate systems during off-hours by incrementally removing enough components to form a second working system, leaving the rest still running the original logged-in users. System software development testing could be done on the second machine, then the components of the second system were added back onto the main user system, without ever having shut it down. Multics supported multiple CPUs: it was one of the earliest multi-processor systems.

Multics was the first major operating system to be designed as a secure system from the ground up. This article describes how security can be achieved through design and engineering Despite this, early versions of Multics were broken into repeatedly. [5] This led to further work that made the system much more secure and prefigured modern security engineering techniques. Security engineering is a specialized field of Engineering that deals with the development of detailed engineering plans and designs for security features controls and systems Break-ins became very rare once the second-generation hardware base was adopted; it had hardware support for ring-oriented security, a multi-level refinement of the concept of master mode.

Multics was the first operating system to provide a hierarchical file system, and filenames could be of almost arbitrary length and syntax; a given file or directory could have multiple names (typically a long and short form); and symbolic links between directories were also supported. It was the first to use the now-standard concept of per-process stacks in the kernel, with a separate stack for each security ring. In computing a process is an instance of a Computer program that is being sequentially executed by a computer system that has the ability to run several computer In Computer science, a stack is an Abstract data type and Data structure based on the principle of Last In First Out (LIFO In Computer science, the kernel is the central component of most computer Operating systems (OS It was also one of the first written in a high level language (PL/I), just after the Burroughs MCP system written in ALGOL. PL/I ("Programming Language One" ˌpiːˌɛlˈwʌn is an imperative computer Programming language designed for scientific engineering The MCP (Master Control Program is the proprietary Operating system of the Burroughs large systems including the Unisys Clearpath/MCP Algol (β Per / Beta Persei known colloquially as the Demon Star, is a bright Star in the Constellation Perseus.

Project history

Multics was developed initially for the GE-645 mainframe, a 36-bit system; later, it was supported on the Honeywell 6180 series machines. The GE-600 series was a family of 36-bit mainframe Computers originating in the 1960s built by General Electric (GE Many early computers aimed at the scientific market had a 36- Bit word length. In 1970 General Electric sold their computing division to Honeywell.

Bell Labs pulled out of the project in 1969; some of the people who had worked on it there went on to create the Unix system. Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer Superficial influence of Multics on Unix is evident in many areas, including the naming of commands. But the design philosophy was quite different, focusing on keeping the system small and simple, and so correcting the perceived deficiencies of Multics. The name "Unix" (originally "Unics") is itself a hack on "Multics". Hack has several meanings in the technology and computer science fields The U in UNIX is rumored to stand for "Uniplexed" as opposed to the "Multiplexed" of Multics, further underscoring the designers' rejections of Multics' complexity in favor of a more straightforward and workable approach.

Honeywell bought GE's computer division, released a better hardware base, and continued system development until 1985. Honeywell ( is a major American multinational conglomerate company that produces a variety of consumer products engineering services and aerospace systems Year 1985 ( MCMLXXXV) was a Common year starting on Tuesday (link displays 1985 Gregorian calendar) About 80 multi-million-dollar sites were installed, at universities, industry, and government sites. The French university system had quite a few in the early 1980s. This article is about the country For a topic outline on this subject see List of basic France topics. The 1980s was the decade spanning from January 1 1980 to December 31 1989. After Honeywell stopped supporting Multics, users migrated to other systems, including Unix. The last Multics machine was shut down on October 31, 2000 at the Canadian Department of National Defence. Events 445 BC – Ezra reads the Book of the Law to the Israelites in Jerusalem (see Nehemiah 91 NLTse 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar.

Multics was distributed in 1975 to 2000 by Groupe Bull in Europe, and by Bull HN Information Systems Inc in the US. Groupe Bull (also known as Bull Information Systems or simply Bull) is a French owned Computer company headquartered in Les Clayes-sous-Bois In 2006 Bull SAS open sourced Multics versions MR10. Open source is a development methodology which offers practical accessibility to a product's source (goods and knowledge 2, MR11. 0, MR12. 0, MR12. 1, MR12. 2, MR12. 3, MR12. 4 & MR12. 5. [6]

Retrospective observations

It is startling that the permanently resident kernel of this powerful multi-processor mainframe computing utility, much derided in its day as being too large and complex, was only 135 kB of code. A kilobyte (derived from the SI prefix Kilo -, meaning 1000 is a unit of Information or Computer storage equal to either 1024 The first MIT GE-645 had 512K words of memory (2 MB), a truly enormous amount at the time, and the kernel only used a moderate portion of Multics main memory. A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on

The entire system, including the operating system and the complex PL/I compiler, user commands, and subroutine libraries, consisted of about 1500 source modules. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another These averaged roughly 200 lines of source code each, and compiled to produce a total of roughly 4. 5 MB of procedure code, which though small today was fairly large by the standards of the day.

Multics compilers generally optimised more for code density than CPU performance, for example using small sub-routines called operators for short standard code-sequences, making direct comparison of object code size with more modern systems less useful. High code density was a good optimisation choice for a multi-user system with expensive main memory, such as Multics. Multi-user is a term that defines an Operating system or Application software that allows concurrent access by multiple users of a Computer.

See also

References

  1. ^ http://www.multicians.org
  2. ^ http://web.mit.edu/multics-history/source/Multics_Internet_Server/Multics_sources.html
  3. ^ http://www.multicians.org/myths.html#source
  4. ^ http://www.multicians.org/myths.html
  5. ^ Tom Van Vleck (2002). Fernando José "Corby" Corbató (born July 1, 1926 in Oakland, California) is a prominent American Computer scientist Jerome H Saltzer (born October 9, 1939 Nampa, Idaho) is a Computer scientist who has made many notable contributions Jack Bonnell Dennis is an American Electrical engineer and a Computer scientist. Peter J Denning is a noted American Computer scientist. He is best known for inventing the working-set model for program behavior which defeated Robert M Graham (born 1929 in the US state of Michigan) is a Computer scientist. Victor A Vyssotsky, son of the Astronomers Alexander N Vyssotsky and Emma Vyssotsky is a Mathematician and Louis Pouzin, (1931 -) born in Chantenay-Saint-Imbert ( Nièvre) France, invented the datagram and designed the first packet communications Peter G Neumann is a researcher who has worked on the Multics operating system in the 1960s Dr Roger R Schell is President of ÆSec a company focused on appliances built on hardened platforms for secure reliable e-business on the Internet Robert Mario Fano (born 1917 as Roberto Mario Fano) is an Italian - American computer scientist currently professor emeritus of Electrical Project MAC (the MIT Project on Mathematics and Computation later the MIT Laboratory for Computer Science ( LCS) was a research laboratory at MIT Joseph Carl Robnett Licklider ( March 11, 1915  &ndash June 26, 1990) known simply as J How the Air Force cracked Multics Security.
  6. ^ http://stuff.mit.edu/afs/athena/reference/multics-history/

Further reading

The literature contains a large number of papers about Multics, and various components of it; a fairly complete list is available here. The most important and/or informative ones are listed below.

Technical details

Security

External links

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